MIPS: BMIPS: Add Whirlwind (BMIPS5200) initialization code

MIPS: BMIPS: Add Whirlwind (BMIPS5200) initialization code

Import bmips_5xxx_init.S from the stblinux-3.3 tree, and to make sure that this
would work nicely with a BMIPS multiplatform kernel (with BMIPS330, BMIPS43XX
and BMIPS5000 enabled), update soft_reset to check for the BMIPS5200 processor
id (PRID_IMP_BMIPS5200) and execute bmips_5xxx_init for these processors to
bring them online.

Tested on 7425, 7429 and 7435 with CPU hotplug. 7435 SMP still needs some
additional changes in the L1 interrupt area to work properly with interrupt
affinity.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: john@phrozen.org
Cc: cernekee@gmail.com
Cc: jon.fraser@broadcom.com
Cc: jaedon.shin@gmail.com
Cc: dragan.stancevic@gmail.com
Cc: jogo@openwrt.org
Patchwork: https://patchwork.linux-mips.org/patch/12377/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>