blk-cgroup: Fix some kernel-doc comments

Make the description of @gendisk to @disk in blkcg_schedule_throttle()
to clear the below warnings:

block/blk-cgroup.c:1850: warning: Function parameter or member 'disk' not described in 'blkcg_schedule_throttle'
block/blk-cgroup.c:1850: warning: Excess function parameter 'gendisk' description in 'blkcg_schedule_throttle'

Fixes: de185b56e8 ("blk-cgroup: pass a gendisk to blkcg_schedule_throttle")
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3338
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221202011713.14834-1-yang.lee@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

@@ -1831,7 +1831,7 @@ out:
 
 /**
  * blkcg_schedule_throttle - this task needs to check for throttling
- * @gendisk: disk to throttle
+ * @disk: disk to throttle
  * @use_memdelay: do we charge this to memory delay for PSI
  *
  * This is called by the IO controller when we know there's delay accumulated