ARM: dts: k2g: Add support for PMMC

ARM: dts: k2g: Add support for PMMC

Enable support for PMMC the TI power processor on K2G. This processor
manages all power management related activities on the SoC and and
allows the Operating Systems on compute processors such as ARM, DSP to
offload the power logic away into the power processor. U-boot just has a
load responsibility, hence the view of the hardware from a bootloader
perspective is different from the view of hardware from a Operating
System perspective. While bootloader just loads up the firmware,
Operating Systems look at the resultant system as "hardware".

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>