reset: add reset controller driver for SCMI agents

reset: add reset controller driver for SCMI agents

This change introduces a reset controller driver for SCMI agent devices.
When SCMI agent and SCMI reset domain drivers are enabled, SCMI agent
binds a reset controller device for each SCMI reset domain protocol
devices enabled in the FDT.

SCMI reset driver is embedded upon CONFIG_RESET_SCMI=y. If enabled,
CONFIG_SCMI_AGENT is also enabled.

SCMI Reset Domain protocol is defined in the SCMI specification [1].

Links: [1] https://developer.arm.com/architectures/system-architectures/software-standards/scmi
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>