MIPS: pm-cps: Add MIPSr6 CPU support

This patch adds support for CPUs implementing the MIPSr6 ISA to the CPS
power management code. Three changes are necessary:

1. In MIPSr6, coupled coherence is necessary when CPUS implement multiple
   Virtual Processors (VPs).

2. MIPSr6 virtual processors are more like real cores and cannot yield
   to other VPs on the same core, so drop the MT ASE yield instruction.

3. To halt a MIPSr6 VP, the CPC VP_STOP register is used rather than the
   MT ASE TCHalt CP0 register.

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: Kees Cook <keescook@chromium.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14225/


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