MAINTAINERS: Add mailing list for SCMI drivers

We have created a new mailing list specific to SCMI. Add it to the
MAINTAINERS file.
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/a9706e17-09ad-4304-828d-c0987befc8f7@moroto.mountainSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

MAINTAINERS

@@ -21798,6 +21798,7 @@ F:	drivers/mfd/syscon.c
 SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE (SCPI/SCMI) Message Protocol drivers
 M:	Sudeep Holla <sudeep.holla@arm.com>
 R:	Cristian Marussi <cristian.marussi@arm.com>
+L:	arm-scmi@vger.kernel.org
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
 F:	Documentation/devicetree/bindings/firmware/arm,sc[mp]i.yaml