MIPS: pm-cps: Change FSB workaround to CPU blacklist

MIPS: pm-cps: Change FSB workaround to CPU blacklist

The check for whether a CPU required the FSB flush workaround
previously required every CPU not requiring it to be whitelisted. That
approach does not scale well as new CPUs are introduced so change the
default from a WARN and returning an error to just returning 0. Any CPUs
requiring the workaround can then be added to the blacklist.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14218/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>