block: Fix blk_mq_*_map_queues() kernel-doc headers

This patch avoids that the kernel-doc script complains about these
function headers when building with W=1.

Cc: Hannes Reinecke <hare@suse.com>
Cc: Keith Busch <keith.busch@intel.com>
Fixes: ed76e329 ("blk-mq: abstract out queue map") # v5.0.
Fixes: e42b3867

 ("blk-mq-rdma: pass in queue map to blk_mq_rdma_map_queues") # v5.0.
Reviewed-by: Chaitanya Kulkarni <chiatanya.kulkarni@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>