MIPS: smp-cps: Avoid BUG() when offlining pre-r6 CPUs

MIPS: smp-cps: Avoid BUG() when offlining pre-r6 CPUs

Commit 0d2808f338c7 ("MIPS: smp-cps: Add support for CPU hotplug of
MIPSr6 processors") added a call to mips_cm_lock_other in order to lock
the CPC in CPUs containing a version 3 or higher Coherence Manager,
which use the general CM core other register, where previous CMs had a
dedicated core other register for the CPC.

A kernel BUG() is triggered, however, if mips_cm_lock_other is called
with a VP other than 0 on a CPU with CM < 3, a condition introduced by
0d2808f338c7.

Avoid the BUG() by always locking VP0 when locking the CPC, since the
required register, cpc_stat_conf, is shared by all vps in a core.

Fixes: 0d2808f338c7 ("MIPS: smp-cps: Add support for CPU hotplug...)
Signed-off-by: Matt Redfearn <[email protected]>
Cc: Qais Yousef <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: James Hogan <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/14297/
Signed-off-by: Ralf Baechle <[email protected]>