HSD#16019035440-4 firmware: stratix10-svc: Return status code for polling service callback (#119)

commit 1da9dcc73b60d49f24a6bb703ce4ffa0963a7b95 from
https://github.com/altera-opensource/linux-socfpga.git socfpga-6.1.55-lts.

The svc_thread_cmd_config_status() function is enhanced to return the
status code from ATF. This is to support new error code for SDOS
decryption from SDM.

Signed-off-by: Teh Wen Ping <wen.ping.teh@intel.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>