mm: hwpoison: fix thp split handing in soft_offline_in_use_page()

When soft_offline_in_use_page() runs on a thp tail page after pmd is
split, we trigger the following VM_BUG_ON_PAGE():

  Memory failure: 0x3755ff: non anonymous thp
  __get_any_page: 0x3755ff: unknown zero refcount page type 2fffff80000000
  Soft offlining pfn 0x34d805 at process virtual address 0x20fff000
  page:ffffea000d360140 count:0 mapcount:0 mapping:0000000000000000 index:0x1
  flags: 0x2fffff80000000()
  raw: 002fffff80000000 ffffea000d360108 ffffea000d360188 0000000000000000
  raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
  page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
  ------------[ cut here ]------------
  kernel BUG at ./include/linux/mm.h:519!

soft_offline_in_use_page() passed refcount and page lock from tail page
to head page, which is not needed because we can pass any subpage to
split_huge_page().

Naoya had fixed a similar issue in c3901e722b29 ("mm: hwpoison: fix thp
split handling in memory_failure()").  But he missed fixing soft
offline.

Link: http://lkml.kernel.org/r/1551452476-24000-1-git-send-email-zhongjiang@huawei.com
Fixes: 61f5d698cc97 ("mm: re-enable THP")
Signed-off-by: zhongjiang <zhongjiang@huawei.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>	[4.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
