blk-mq: rename blk_mq_sysfs_{,un}register

Add a _hctx postfix to better describe what the functions do, match
the debugfs equivalents and release the old names for functions that
should be using them.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220628171850.1313069-6-hch@lst.de


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