mm/memory-failure.c: minor clean up for memory_failure_dev_pagemap

mm/memory-failure.c: minor clean up for memory_failure_dev_pagemap

Patch series "A few cleanup and fixup patches for memory failure", v3.

This series contains a few patches to simplify the code logic, remove
unneeded variable and remove obsolete comment.  Also we fix race changing
page more robustly in memory_failure.  More details can be found in the
respective changelogs.

This patch (of 8):

The flags always has MF_ACTION_REQUIRED and MF_MUST_KILL set.  So we do
not need to check these flags again.

Link: https://lkml.kernel.org/r/20220218090118.1105-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220218090118.1105-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>