mm/memory-failure.c: add hwpoison_filter for soft offline

mm/memory-failure.c: add hwpoison_filter for soft offline

hwpoison_filter is missing in the soft offline path, this leads an issue:
after enabling the corrupt filter, the user process still has a chance to
inject hwpoison fault by madvise(addr, len, MADV_SOFT_OFFLINE) at PFN
which is expected to reject.

Also do a minor change in comment of memory_failure().

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: zhenwei pi <[email protected]>
Acked-by: Naoya Horiguchi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>