Make mbedtls_sa_ecp_load_public_part return psa_status_t

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 927b9d4..2c6f108 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3787,10 +3787,10 @@
         return status;
     }
 
-    int ret = mbedtls_psa_ecp_load_public_part(operation->ctx);
+    status = mbedtls_psa_ecp_load_public_part(operation->ctx);
 
-    if (ret != 0) {
-        return mbedtls_to_psa_error(ret);
+    if (status != PSA_SUCCESS) {
+        return status;
     }
 
     /* We only need to store the same length of hash as the private key size