Revert "userfaultfd: selftest: vm: allow to build in vm/ directory"

Revert "userfaultfd: selftest: vm: allow to build in vm/ directory"

This reverts commit b5213e1e9f25ccde958aa6364815ee87fef91100 which was
commit 46aa6a302b53f543f8e8b8e1714dc5e449ad36a6 upstream.

This is being reverted because the affected commit this was trying to
fix, a8ba798bc8ec ("selftests: enable O and KBUILD_OUTPUT"), was never
backported to the 4.4-stable tree.

Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>