mm: drop zap_details::ignore_dirty

The only user of ignore_dirty is oom-reaper.  But it doesn't really use
it.

ignore_dirty only has effect on file pages mapped with dirty pte.  But
oom-repear skips shared VMAs, so there's no way we can dirty file pte in
them.

Change-Id: Ife5733540fd14e5276a275d91fb46ee490b6aee0
Link: http://lkml.kernel.org/r/20170118122429.43661-1-kirill.shutemov@linux.intel.com


Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-Commit: da162e9368990ed747075e2ab427da0759fc4a59
Git-Repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git


Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>