fix(drtm): return proper values for DRTM get and set error SMCs

The DRTM get and set error previously returned SMC_UNK when these
SMCs were issued. This has been corrected to return an appropriate
error code on failure, and success otherwise.
Also,align the error code values with the specification.

Change-Id: I8f11f94f1ab097245003dbde97365fa54e0097ba
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/services/std_svc/drtm/drtm_main.c b/services/std_svc/drtm/drtm_main.c
index b9c83fa..53afb17 100644
--- a/services/std_svc/drtm/drtm_main.c
+++ b/services/std_svc/drtm/drtm_main.c
@@ -808,12 +808,12 @@
 
 	case ARM_DRTM_SVC_GET_ERROR:
 		INFO("DRTM service handler: get error\n");
-		drtm_get_error(handle);
+		return drtm_get_error(handle);
 		break;	/* not reached */
 
 	case ARM_DRTM_SVC_SET_ERROR:
 		INFO("DRTM service handler: set error\n");
-		drtm_set_error(x1, handle);
+		return drtm_set_error(x1, handle);
 		break;	/* not reached */
 
 	case ARM_DRTM_SVC_SET_TCB_HASH:
diff --git a/services/std_svc/drtm/drtm_remediation.c b/services/std_svc/drtm/drtm_remediation.c
index 696b4ea..81d27ec 100644
--- a/services/std_svc/drtm/drtm_remediation.c
+++ b/services/std_svc/drtm/drtm_remediation.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Arm Limited. All rights reserved.
+ * Copyright (c) 2022-2024 Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier:    BSD-3-Clause
  *
@@ -21,7 +21,7 @@
 	rc = plat_set_drtm_error(x1);
 
 	if (rc != 0) {
-		SMC_RET1(ctx, INTERNAL_ERROR);
+		SMC_RET1(ctx, NOT_FOUND);
 	}
 
 	SMC_RET1(ctx, SUCCESS);
@@ -35,7 +35,7 @@
 	rc = plat_get_drtm_error(&error_code);
 
 	if (rc != 0) {
-		SMC_RET1(ctx, INTERNAL_ERROR);
+		SMC_RET1(ctx, NOT_FOUND);
 	}
 
 	SMC_RET2(ctx, SUCCESS, error_code);