HWPOISON: check dirty flag to match against clean page

Currently page_action() does not check dirty flag to determine whether
the error page is "clean mlocked/unevictable LRU" page.  This doesn't
cause any misjudgement because we do matching against "dirty
mlocked/unevictable LRU" just before the check.  But in order to make
code consistent and/or to avoid potential regression, we had better
check dirty flag explicitly.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Suggested-by: Chen Gong <gong.chen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>