revert "proc: clear_refs: do not clear reserved pages"

Revert commit 85e72aa5 ("proc: clear_refs: do not clear reserved
pages"), which was a quick fix suitable for -stable until ARM had been
moved over to the gate_vma mechanism:

https://lkml.org/lkml/2012/1/14/55



With commit f9d4861f ("ARM: 7294/1: vectors: use gate_vma for vectors user
mapping"), ARM does now use the gate_vma, so the PageReserved check can be
removed from the proc code.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Nicolas Pitre <nico@linaro.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>