blk-cgroup: fix kernel-doc warnings in header file

Correct the function parameters and function names to eliminate
kernel-doc warnings:

blk-cgroup.h:238: warning: Function parameter or struct member 'bio' not described in 'bio_issue_as_root_blkg'
blk-cgroup.h:248: warning: bad line:
blk-cgroup.h:279: warning: expecting prototype for blkg_to_pdata(). Prototype was for blkg_to_pd() instead
blk-cgroup.h:296: warning: expecting prototype for pdata_to_blkg(). Prototype was for pd_to_blkg() instead

Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Cc: Josef Bacik <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-cgroup.h

···
 
 /**
  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
- * @return: true if this bio needs to be submitted with the root blkg context.
+ * @bio: the target &bio
+ *
+ * Return: true if this bio needs to be submitted with the root blkg context.
  *
  * In order to avoid priority inversions we sometimes need to issue a bio as if
  * it were attached to the root blkg, and then backcharge to the actual owning
···
  * @q: request_queue of interest
  *
  * Lookup blkg for the @blkcg - @q pair.
-
+ *
  * Must be called in a RCU critical section.
  */
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
···
 }
 
 /**
- * blkg_to_pdata - get policy private data
+ * blkg_to_pd - get policy private data
  * @blkg: blkg of interest
  * @pol: policy of interest
  *
···
 }
 
 /**
- * pdata_to_blkg - get blkg associated with policy private data
+ * pd_to_blkg - get blkg associated with policy private data
  * @pd: policy private data of interest
  *
  * @pd is policy private data.  Determine the blkg it's associated with.