mm/memcontrol.c: fix bad line in comment

Commit 23067153 ("mm: memory.low hierarchical behavior") missed an
asterisk in one of the comments.

  mm/memcontrol.c:5774: warning: bad line:                | 0, otherwise.

Link: http://lkml.kernel.org/r/20190301143734.94393-1-cai@lca.pwAcked-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -5752,7 +5752,7 @@ struct cgroup_subsys memory_cgrp_subsys = {
  *
  *             | memory.current, if memory.current < memory.low
  * low_usage = |
-	       | 0, otherwise.
+ *	       | 0, otherwise.
  *
  *
  * Such definition of the effective memory.low provides the expected