selftests: clone3: clone3: add case CLONE3_ARGS_NO_TEST

Building selftests/clone3 with clang warns about enumeration not handled
in switch case:

clone3.c:54:10: warning: enumeration value 'CLONE3_ARGS_NO_TEST' not handled in switch [-Wswitch]
        switch (test_mode) {
                ^

Add the missing switch case with a comment.

Fixes: 17a81069 ("selftests: add tests for clone3()")
Signed-off-by: NAnders Roxell <anders.roxell@linaro.org>
Acked-by: NChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: NShuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/clone3/clone3.c

@@ -52,6 +52,12 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
 		size = sizeof(struct __clone_args);
 
 	switch (test_mode) {
+	case CLONE3_ARGS_NO_TEST:
+		/*
+		 * Uses default 'flags' and 'SIGCHLD'
+		 * assignment.
+		 */
+		break;
 	case CLONE3_ARGS_ALL_0:
 		args.flags = 0;
 		args.exit_signal = 0;