block: move three bvec helpers declaration into private helper

bvec_alloc(), bvec_free() and bvec_nr_vecs() are only used inside block
layer core functions, no need to declare them in public header.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk.h

@@ -55,6 +55,10 @@ void blk_free_flush_queue(struct blk_flush_queue *q);
 
 void blk_freeze_queue(struct request_queue *q);
 
+struct bio_vec *bvec_alloc(gfp_t, int, unsigned long *, mempool_t *);
+void bvec_free(mempool_t *, struct bio_vec *, unsigned int);
+unsigned int bvec_nr_vecs(unsigned short idx);
+
 static inline bool biovec_phys_mergeable(struct request_queue *q,
 		struct bio_vec *vec1, struct bio_vec *vec2)
 {

include/linux/bio.h

@@ -478,9 +478,6 @@ static inline void zero_fill_bio(struct bio *bio)
 	zero_fill_bio_iter(bio, bio->bi_iter);
 }
 
-extern struct bio_vec *bvec_alloc(gfp_t, int, unsigned long *, mempool_t *);
-extern void bvec_free(mempool_t *, struct bio_vec *, unsigned int);
-extern unsigned int bvec_nr_vecs(unsigned short idx);
 extern const char *bio_devname(struct bio *bio, char *buffer);
 
 #define bio_set_dev(bio, bdev) 				\