block: cleanup ioc_clear_queue

Fold __ioc_clear_queue into ioc_clear_queue and switch to always
use plain _irq locking instead of the more expensive _irqsave that
is not needed here.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211209063131.18537-7-hch@lst.de


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