intel: Update RSU driver return code

Modify RSU driver error code for backward-compatibility with
Linux RSU driver

Signed-off-by: Abdul Halim, Muhammad Hadi Asyrafi <muhammad.hadi.asyrafi.abdul.halim@intel.com>
Change-Id: Ib9e38d4017efe35d3aceeee27dce451fbd429fb5
diff --git a/plat/intel/soc/common/socfpga_sip_svc.c b/plat/intel/soc/common/socfpga_sip_svc.c
index 1c3d45b..b15fa3d 100644
--- a/plat/intel/soc/common/socfpga_sip_svc.c
+++ b/plat/intel/soc/common/socfpga_sip_svc.c
@@ -374,7 +374,7 @@
 static uint32_t intel_rsu_status(uint64_t *respbuf, uint32_t respbuf_sz)
 {
 	if (mailbox_rsu_status((uint32_t *)respbuf, respbuf_sz) < 0)
-		return INTEL_SIP_SMC_STATUS_ERROR;
+		return INTEL_SIP_SMC_RSU_ERROR;
 
 	return INTEL_SIP_SMC_STATUS_OK;
 }
@@ -388,7 +388,7 @@
 static uint32_t intel_rsu_notify(uint64_t execution_stage)
 {
 	if (mailbox_hps_stage_notify(execution_stage) < 0)
-		return INTEL_SIP_SMC_STATUS_ERROR;
+		return INTEL_SIP_SMC_RSU_ERROR;
 
 	return INTEL_SIP_SMC_STATUS_OK;
 }
@@ -397,7 +397,7 @@
 					uint32_t *ret_stat)
 {
 	if (mailbox_rsu_status((uint32_t *)respbuf, respbuf_sz) < 0)
-		return INTEL_SIP_SMC_STATUS_ERROR;
+		return INTEL_SIP_SMC_RSU_ERROR;
 
 	*ret_stat = respbuf[8];
 	return INTEL_SIP_SMC_STATUS_OK;