blk-mq: move the cache friendly bitmap type of out blk-mq-tag

We will use it for the pending list in blk-mq core as well.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --cc block/blk-mq-tag.c
Simple merge

diff --cc block/blk-mq-tag.h
Simple merge

diff --cc block/blk-mq.h
Simple merge