mm: Fix fixup_user_fault() for MMU=n

mm: Fix fixup_user_fault() for MMU=n

commit 5c723ba5b7886909b2e430f2eae454c33f7fe5c6 upstream.

In commit 2efaca927f5c ("mm/futex: fix futex writes on archs with SW
tracking of dirty & young") we forgot about MMU=n.  This patch fixes
that.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/1311761831.24752.413.camel@twins
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>