mm: memory-failure: avoid pfn_valid() twice in soft_offline_page()

Simplify WARN_ON_ONCE(flags & MF_COUNT_INCREASED) under !pfn_valid().

Link: https://lkml.kernel.org/r/20221021084611.53765-2-wangkefeng.wang@huawei.com


Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>