Fix control may reach end of non-void function error

cli/x52_cli.c

@@ -326,6 +326,8 @@ static int do_help(const struct command_handler *cmd)
 
         printf("\nWARNING: raw command may damage your device\n\n");
     }
+
+    return 0;
 }
 
 int main(int argc, char **argv)

test/x52_test_led.c

@@ -75,4 +75,6 @@ int test_blink_n_shift(void)
 
     TEST_BLINK_OR_SHIFT(blink);
     TEST_BLINK_OR_SHIFT(shift);
+
+    return 0;
 }