mm: memcontrol: eliminate redundant check in __mem_cgroup_insert_exceeded()

The mz->usage_in_excess >= mz_node->usage_in_excess check is exactly the
else case of mz->usage_in_excess < mz_node->usage_in_excess.  So we could
replace else if (mz->usage_in_excess >= mz_node->usage_in_excess) with
else equally.  Also drop the comment which doesn't really explain much.

Link: https://lkml.kernel.org/r/20201012131607.10656-1-linmiaohe@huawei.com


Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>