common: command: Use command_ret_t enum values instead of values

Use enum command_ret_t types in cmd_process_error().
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>
Reviewed-by: NSimon Glass <sjg@chromum.org>

common/command.c

@@ -549,8 +549,8 @@ int cmd_process_error(cmd_tbl_t *cmdtp, int err)
 {
 	if (err) {
 		printf("Command '%s' failed: Error %d\n", cmdtp->name, err);
-		return 1;
+		return CMD_RET_FAILURE;
 	}
 
-	return 0;
+	return CMD_RET_SUCCESS;
 }