nds32: Fix a kernel panic issue because of wrong frame pointer access.

nds32: Fix a kernel panic issue because of wrong frame pointer access.

It can make sure that trace_hardirqs_off/trace_hardirqs_on can get a correct
return address by frame pointer through __builtin_return_address() in this fix.

Unable to handle kernel paging request at virtual address fffffffc
pgd = 3c42e9cf
[fffffffc] *pgd=02a9c000

Internal error: Oops: 1 [#1]
Modules linked in:
CPU: 0
PC is at trace_hardirqs_off+0x78/0xec
LP is at common_exception_handler+0xda/0xf4
pc : [<b23ea5a4>]    lp : [<b2352eba>]    Tainted: G        W
sp : ada60ab0  fp : efcaff48  gp : 3a020490
r25: efcb0000  r24: 00000000
r23: 00000000  r22: 00000000  r21: 00000000  r20: 000700c1
r19: 000700ca  r18: 3a21b018  r17: 00000001  r16: 00000002
r15: 00000001  r14: 0000002a  r13: 3a00a804  r12: ada60ab0
r11: 3a113af8  r10: 3a01c530  r9 : 3a124404  r8 : 00120f9c
r7 : b2352eba  r6 : 00000000  r5 : 3a126b58  r4 : 00000000
r3 : 3a1726a8  r2 : b2921000  r1 : 00000000  r0 : 00000000
  IRQs off  Segment user
Process init (pid: 1, stack limit = 0x069d7f15)
Stack: (0xada60ab0 to 0xada61000)
Stack: 0aa0:                                     00000000 00000003 3a110000 0011f000
Stack: 0ac0: 00000005 00000000 00000000 00000000 ada60b10 3a01fe68 ada60b0c ada60b08
Stack: 0ae0: 00000000 ada60ab8 ada60b30 3a020550 00000000 00000001 3a11c2f8 3a01c6e8
Stack: 0b00: 3a01cb80 fffffba8 3a113af8 3a21b018 3a122c28 00003ec4 00000165 00000000
Stack: 0b20: 3a126aec 0000006c 00000000 00000001 3a01fe68 00000000 00000003 00000000
Stack: 0b40: 00000001 000003f8 3a020930 3a01c530 00000008 ada60c18 3a020490 3a003120
Stack: 0b60: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0b80: 00000000 00000000 00000000 00000000 ffff8000 00000000 00000000 00000000
Stack: 0ba0: 00000000 00000001 3a020550 00000000 3a01d020 00000000 fffff000 fffff000
Stack: 0bc0: 00000000 00000000 00000000 00000000 ada60f2c 00000000 00000001 00000000
Stack: 0be0: 00000000 00000000 3a01fe68 fffffab0 00008034 00000008 3a0010cc 3a01fe68
Stack: 0c00: 00000000 00000000 00000001 ada60c88 3a020490 3a0139d4 0009dc6f 00000000
Stack: 0c20: 00000000 00000000 ada60fce fffff000 00000000 0000ebe0 3a020038 3a020550
Stack: 0c40: ada60f20 ada60c90 3a0007f0 3a0002a8 ada60c8c 00000000 00000000 ada60c88
Stack: 0c60: 3a020490 3a004570 00000000 00000000 ada60f20 3a0007f0 3a000000 00000000
Stack: 0c80: 3a020490 3a004850 00000000 3a013f24 3a000000 00000000 3a01ff44 00000000
Stack: 0ca0: 00000000 00000000 00000000 00000000 00000000 00000000 3a01ff84 3a01ff7c
Stack: 0cc0: 3a01ff4c 3a01ff5c 3a01ff64 3a01ff9c 3a01ffa4 3a01ffac 3a01ff6c 3a01ff74
Stack: 0ce0: 00000000 00000000 3a01ff44 00000000 00000000 00000000 00000000 00000000
Stack: 0d00: 3a01ff8c 00000000 00000000 3a01ff94 00000000 00000000 00000000 00000000
Stack: 0d20: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0d40: 3a01ffbc 3a01ffb4 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0d60: 00000000 00000000 00000000 00000000 00000000 3a01ffc4 00000000 00000000
Stack: 0d80: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0da0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0dc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 3a01ff54
Stack: 0de0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0e00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0e20: 00000000 00000004 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0e40: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0e60: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0e80: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0ea0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Stack: 0ec0: 00000000 00000000 00000000 00000000 ffffffff 00000000 00000000 00000000
Stack: 0ee0: 00000000 00000000 00000000 00000000 ada60f20 00000000 00000000 00000000
Stack: 0f00: 00000000 00000000 00000000 00000000 00000000 00000000 3a020490 3a000b24
Stack: 0f20: 00000001 ada60fde 00000000 ada60fe4 ada60feb 00000000 00000021 3a038000
Stack: 0f40: 00000010 0009dc6f 00000006 00001000 00000011 00000064 00000003 00008034
Stack: 0f60: 00000004 00000020 00000005 00000008 00000007 3a000000 00000008 00000000
Stack: 0f80: 00000009 0000ebe0 0000000b 00000000 0000000c 00000000 0000000d 00000000
Stack: 0fa0: 0000000e 00000000 00000017 00000000 00000019 ada60fce 0000001f ada60ff6
Stack: 0fc0: 00000000 00000000 00000000 b5010000 fa839914 23b5dd89 a2aea540 692fc82e
Stack: 0fe0: 0074696e 454d4f48 54002f3d 3d4d5245 756e696c 692f0078 0074696e 00000000
CPU: 0 PID: 1 Comm: init Tainted: G        W         4.18.0-00015-g1888b64a2558-dirty #112
Hardware name: andestech,ae3xx (DT)
Call Trace:
[<b27a8e34>] dump_stack+0x2c/0x38
[<b2354874>] die+0x128/0x18c
[<b2356f4c>] do_page_fault+0x3b8/0x4e0
[<b2352ed4>] ret_from_exception+0x0/0x10
[<b2352eba>] common_exception_handler+0xda/0xf4

Signed-off-by: Greentime Hu <greentime@andestech.com>