mm/memory-failure.c: clean up soft_offline_page()

mm/memory-failure.c: clean up soft_offline_page()

Currently soft_offline_page() is hard to maintain because it has many
return points and goto statements.  All of this mess come from
get_any_page().  This function should only get page refcount as the name
implies, but it does some page isolating actions like SetPageHWPoison()
and dequeuing hugepage.  This patch corrects it and introduces some
internal subroutines to make soft offlining code more readable and
maintainable.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>