net: hns: Fix use after free identified by SLUB debug

net: hns: Fix use after free identified by SLUB debug

When enable SLUB debug, than remove hns_enet_drv module, SLUB debug will
identify a use after free bug:

[134.189505] Unable to handle kernel paging request at virtual address
		006b6b6b6b6b6b6b
[134.197553] Mem abort info:
[134.200381]   ESR = 0x96000004
[134.203487]   Exception class = DABT (current EL), IL = 32 bits
[134.209497]   SET = 0, FnV = 0
[134.212596]   EA = 0, S1PTW = 0
[134.215777] Data abort info:
[134.218701]   ISV = 0, ISS = 0x00000004
[134.222596]   CM = 0, WnR = 0
[134.225606] [006b6b6b6b6b6b6b] address between user and kernel address ranges
[134.232851] Internal error: Oops: 96000004 [#1] SMP
[134.237798] CPU: 21 PID: 27834 Comm: rmmod Kdump: loaded Tainted: G
		OE     4.19.5-1.2.34.aarch64 #1
[134.247856] Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.58 10/24/2018
[134.255181] pstate: 20000005 (nzCv daif -PAN -UAO)
[134.260044] pc : hns_ae_put_handle+0x38/0x60
[134.264372] lr : hns_ae_put_handle+0x24/0x60
[134.268700] sp : ffff00001be93c50
[134.272054] x29: ffff00001be93c50 x28: ffff802faaec8040
[134.277442] x27: 0000000000000000 x26: 0000000000000000
[134.282830] x25: 0000000056000000 x24: 0000000000000015
[134.288284] x23: ffff0000096fe098 x22: ffff000001050070
[134.293671] x21: ffff801fb3c044a0 x20: ffff80afb75ec098
[134.303287] x19: ffff80afb75ec098 x18: 0000000000000000
[134.312945] x17: 0000000000000000 x16: 0000000000000000
[134.322517] x15: 0000000000000002 x14: 0000000000000000
[134.332030] x13: dead000000000100 x12: ffff7e02bea3c988
[134.341487] x11: ffff80affbee9e68 x10: 0000000000000000
[134.351033] x9 : 6fffff8000008101 x8 : 0000000000000000
[134.360569] x7 : dead000000000100 x6 : ffff000009579748
[134.370059] x5 : 0000000000210d00 x4 : 0000000000000000
[134.379550] x3 : 0000000000000001 x2 : 0000000000000000
[134.388813] x1 : 6b6b6b6b6b6b6b6b x0 : 0000000000000000
[134.397993] Process rmmod (pid: 27834, stack limit = 0x00000000d474b7fd)
[134.408498] Call trace:
[134.414611]  hns_ae_put_handle+0x38/0x60
[134.422208]  hnae_put_handle+0xd4/0x108
[134.429563]  hns_nic_dev_remove+0x60/0xc0 [hns_enet_drv]
[134.438342]  platform_drv_remove+0x2c/0x70
[134.445958]  device_release_driver_internal+0x174/0x208
[134.454810]  driver_detach+0x70/0xd8
[134.461913]  bus_remove_driver+0x64/0xe8
[134.469396]  driver_unregister+0x34/0x60
[134.476822]  platform_driver_unregister+0x20/0x30
[134.485130]  hns_nic_dev_driver_exit+0x14/0x6e4 [hns_enet_drv]
[134.494634]  __arm64_sys_delete_module+0x238/0x290

struct hnae_handle is a member of struct hnae_vf_cb, so when vf_cb is
freed, than use hnae_handle will cause use after free panic.

This patch frees vf_cb after hnae_handle used.

Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>