block: move blk_account_io_{start,done} to blk-mq.c

These are only used for request based I/O, so move them where they are
used.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20211117061404.331732-9-hch@lst.de


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