dt-bindings: power: Convert mti,mips-cpc to DT schema

It's a Cluster Power Controller embedded into the MIPS IP cores.
Currently the corresponding dts node is supposed to have compatible
and reg properties.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>