mm/memcg: Remove 'page' parameter to mem_cgroup_charge_statistics()

The last use of 'page' was removed by commit 468c3982 ("mm:
memcontrol: switch to native NR_ANON_THPS counter"), so we can now remove
the parameter from the function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>