imx: add sip function

Add SiP (Silicon Provider) services function to issue
SMC call to Arm Trusted Firmware.

More SiP information could be found in
  https://github.com/ARM-software/arm-trusted-firmware/blob/master/


  docs/arm-sip-service.rst

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>