ARM: dts: k2g: Add TI SCI reset-controller node

Add a reset-controller node for managing resets of various
remote processor devices on the SoC over the Texas Instrument's
System Control Interface (TI SCI) protocol.

Signed-off-by: Andrew F. Davis <afd@ti.com>
[s-anna@ti.com: revise commit description slightly]
Signed-off-by: Suman Anna <s-anna@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>