selftest: fix build error in tools/testing/selftests/vm/userfaultfd.c

When backporting 0db282b ("selftest: use mmap instead of
posix_memalign to allocate memory") to this stable branch, I forgot a {
breaking the build.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/testing/selftests/vm/userfaultfd.c

@@ -182,7 +182,7 @@ static void anon_allocate_area(void **alloc_area)
 {
 	*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
 			   MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
-	if (*alloc_area == MAP_FAILED)
+	if (*alloc_area == MAP_FAILED) {
 		fprintf(stderr, "mmap of anonymous memory failed");
 		*alloc_area = NULL;
 	}