buffer: remove useless comment and WB_REASON_FREE_MORE_MEM, reason.
free_more_memory func has been completely removed in commit
bc48f001de12
("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: bc48f001de12 ("buffer: eliminate the need to call free_more_memory() in __getblk_slow()")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>