Commit 6b208e3f ("mm: memcg: remove unused node/section info from
pc->flags") deleted lookup_cgroup_page() but left a prototype for it.

Kill the vestigial prototype.
Signed-off-by: NGreg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>