mm: soft-offline: dissolve free hugepage if soft-offlined

Now we have code to rescue most of healthy pages from a hwpoisoned
hugepage.  So let's apply it to soft_offline_free_page too.

Link: http://lkml.kernel.org/r/1496305019-5493-6-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>