MIPS: pm-cps: Support CM3 changes to Coherence Enable Register

MIPS CM3 changed the management of coherence. Instead of a coherence
control register with a bitmask of coherent domains, CM3 simply has a
coherence enable register with a single bit to enable coherence of the
local core. Support this by clearing and setting this single bit to
disable / enable coherence.

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: Tony Wu <tung7970@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Nikolay Martynov <mar.kolya@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14226/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>