arm: socfpga: smc: Add function to get usercode

Add function to send mailbox command via SMC to get usercode from SDM.

Signed-off-by: Siew Chin Lim <elly.siew.chin.lim@intel.com>
Reviewed-by: Ley Foon Tan <ley.foon.tan@intel.com>
3 files changed