Fix wrong return statement

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 4802732..441089f 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -6623,8 +6623,8 @@
 
 exit:
     mbedtls_sha256_free(&sha256);
+    return ret;
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
-    return 0;
 }
 #endif /* MBEDTLS_HAS_ALG_SHA_256_VIA_MD_OR_PSA_BASED_ON_USE_PSA */