rtc: imx-sc: add rtc set time support

This patch adds i.MX system controller RTC set time support, the
RTC set time is implemented via SIP(silicon provider) runtime
service call and ARM-Trusted-Firmware will communicate with system
controller via MU(message unit) IPC to set RTC time.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>