Texas Instrument's System Control Interface (TI-SCI) Message Protocol
is used in Texas Instrument's System on Chip (SoC) such as those
in K3 family AM654x SoCs to communicate between various compute
processors with a central system controller entity.

TI-SCI message protocol provides support for management of various
hardware entities within the SoC. Add support driver to allow
communication with system controller entity within the SoC.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Andreas Dannenberg <dannenberg@ti.com>