selftests/mm: mkdirty: fix incorrect position of #endif

selftests/mm: mkdirty: fix incorrect position of #endif

The #endif is the wrong side of a } causing a build failure when
__NR_userfaultfd is not defined.  Fix this by moving the #end to enclose
the }

Link: https://lkml.kernel.org/r/20230712134648.456349-1-colin.i.king@gmail.com
Fixes: 9eac40fc0cc7 ("selftests/mm: mkdirty: test behavior of (pte|pmd)_mkdirty on VMAs without write permissions")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>