Merge: selftests/memfd/memfd_test: fix possible NULL pointer dereference

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/984

Fix undefined behavior by backporting the following upstream commit:

```
    commit 73519de
    Author: liuye <liuye@kylinos.cn>
    Date:   Tue Jan 14 11:21:15 2025 +0800

        selftests/memfd/memfd_test: fix possible NULL pointer dereference

        If `name' is NULL, a NULL pointer may be accessed in printf.
```

JIRA: https://issues.redhat.com/browse/RHEL-94834

Signed-off-by: Joel Savitz <jsavitz@redhat.com>

Approved-by: Waiman Long <longman@redhat.com>
Approved-by: Herton R. Krzesinski <herton@redhat.com>
Approved-by: Rafael Aquini <raquini@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Jan Stancek <jstancek@redhat.com>

Author: jstancek

tools/testing/selftests/memfd/memfd_test.c

@@ -170,7 +170,7 @@ static void mfd_fail_new(const char *name, unsigned int flags)
 	r = sys_memfd_create(name, flags);
 	if (r >= 0) {
 		printf("memfd_create(\"%s\", %u) succeeded, but failure expected\n",
-		       name, flags);
+		       name ? name : "NULL", flags);
 		close(r);
 		abort();
 	}