blk-cgroup: Remove unused declaration blkg_path()

Commit bb7e5a19 ("block, bfq: remove blkg_path()") removed the
implementation but leave declaration.
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20240816095821.877842-1-yuehaibing@huawei.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.h

@@ -485,7 +485,6 @@ static inline void blkcg_deactivate_policy(struct gendisk *disk,
 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 						  struct blkcg_policy *pol) { return NULL; }
 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
-static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
 static inline void blkg_get(struct blkcg_gq *blkg) { }
 static inline void blkg_put(struct blkcg_gq *blkg) { }
 static inline void blkcg_bio_issue_init(struct bio *bio) { }