block: remove bvec_kmap_irq and bvec_kunmap_irq

These two helpers are entirely unused now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727055646.118787-10-hch@lst.de


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