mm/memory-failure: convert unpoison_memory() to folios

Use a folio inside unpoison_memory which replaces a compound_head() call
with a call to page_folio().

Link: https://lkml.kernel.org/r/20230112204608.80136-9-sidhartha.kumar@oracle.com


Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>