mm/hwpoison: fix some obsolete comments

Since commit cb731d6c ("vmscan: per memory cgroup slab shrinkers"),
shrink_node_slabs is renamed to drop_slab_node.  And doit argument is
changed to forcekill since commit 6751ed65 ("x86/mce: Fix
siginfo_t->si_addr value for non-recoverable memory faults").

Link: https://lkml.kernel.org/r/20210814105131.48814-5-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: Linus Torvalds <torvalds@linux-foundation.org>