mm/page_counter: correct the obsolete func name in the comment of page_counter_try_ch...

mm/page_counter: correct the obsolete func name in the comment of page_counter_try_charge()

Since commit bbec2e15170a ("mm: rename page_counter's count/limit into
usage/max"), page_counter_limit() is renamed to page_counter_set_max().
So replace page_counter_limit with page_counter_set_max in comment.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20200917113629.14382-1-linmiaohe@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>