block: remove unused parameter

The blk_mq_map_queue()'s request_queue param is not used anymore,
remove it, same with blk_get_flush_queue().

Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250312084722.129680-1-kanie@linux.alibaba.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>