pagemap: remove wait_on_page_locked_killable()

There is no users of wait_on_page_locked_killable(), remove it.

Link: https://lkml.kernel.org/r/20230815030609.39313-1-wangkefeng.wang@huawei.com


Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>