sysreset: Add TI System Control Interface (TI SCI) sysreset driver

sysreset: Add TI System Control Interface (TI SCI) sysreset driver

Devices from the TI K3 family of SoCs like the AM654x contain a Device
Management and Security Controller (SYSFW) that manages the low-level
device control (like clocks, resets etc) for the various hardware
modules present on the SoC. These device control operations are provided
to the host processor OS through a communication protocol called the TI
System Control Interface (TI SCI) protocol.

This patch adds a system reset driver that communicates to the system
controller over the TI SCI protocol for allowing to perform a system-
wide SoC reset.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>