tools/testing/selftests: fix gup_longterm for unknown fs

Commit 66bce7a ("selftests/mm: fix test result reporting in
gup_longterm") introduced a small bug causing unknown filesystems to
always result in a test failure.

This is because do_test() was updated to use a common reporting path, but
this case appears to have been missed.

This is problematic for e.g.  virtme-ng which uses an overlayfs file
system, causing gup_longterm to appear to fail each time due to a test
count mismatch:

	# Planned tests != run tests (50 != 46)
	# Totals: pass:24 fail:0 xfail:0 xpass:0 skip:22 error:0

The fix is to simply change the return into a break.

Link: https://lkml.kernel.org/r/20260106154547.214907-1-lorenzo.stoakes@oracle.com
Fixes: 66bce7a ("selftests/mm: fix test result reporting in gup_longterm")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: ljskernel

tools/testing/selftests/mm/gup_longterm.c

@@ -179,7 +179,7 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
 		if (rw && shared && fs_is_unknown(fs_type)) {
 			ksft_print_msg("Unknown filesystem\n");
 			result = KSFT_SKIP;
-			return;
+			break;
 		}
 		/*
 		 * R/O pinning or pinning in a private mapping is always