remoteproc: Add support for TI power processor

remoteproc: Add support for TI power processor

Many TI System on Chip (SoC) solutions do have a dedicated
microcontroller for doing power management functionality. These include
the AM335x, AM437x, Keystone K2G SoCs. The functionality provided by
these microcontrollers and the communication mechanisms vary very
widely. However, we are able to consolidate some basic functionality to
be generic enough starting with K2G SoC family. Introduce a basic remote
proc driver to support these microcontrollers. In fact, on SoCs starting
with K2G, basic power management functions are primarily accessible for
the High Level Operating Systems(HLOS) via these microcontroller solutions.

Hence, having these started at a bootloader level is pretty much
mandatory.

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