block: Fix rq_qos_wait() kernel-doc header

Add documentation for the @rqw argument and change " - " into ": ".

Fixes: 84f60324 ("block: add rq_qos_wait to rq_qos") # v5.0-rc1~52^2~140.
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>

block/blk-rq-qos.c

@@ -209,9 +209,10 @@ static int rq_qos_wake_function(struct wait_queue_entry *curr,
 
 /**
  * rq_qos_wait - throttle on a rqw if we need to
- * @private_data - caller provided specific data
- * @acquire_inflight_cb - inc the rqw->inflight counter if we can
- * @cleanup_cb - the callback to cleanup in case we race with a waker
+ * @rqw: rqw to throttle on
+ * @private_data: caller provided specific data
+ * @acquire_inflight_cb: inc the rqw->inflight counter if we can
+ * @cleanup_cb: the callback to cleanup in case we race with a waker
  *
  * This provides a uniform place for the rq_qos users to do their throttling.
  * Since you can end up with a lot of things sleeping at once, this manages the