free_more_memory func has been completely removed in commit bc48f001
("buffer: eliminate the need to call free_more_memory() in __getblk_slow()")

So comment and `WB_REASON_FREE_MORE_MEM` reason about free_more_memory
are no longer needed.

Fixes: bc48f001 ("buffer: eliminate the need to call free_more_memory() in __getblk_slow()")
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NZhiqiang Liu <liuzhiqiang26@huawei.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>