block: remove bio_clone_bioset_partial()

commit c18a1e0(block: introduce bio_clone_bioset_partial()) introduced
bio_clone_bioset_partial() for raid1 write behind IO. Now the write behind is
rewritten by Ming. We don't need the API any more, so revert the commit.

Cc: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 42b62a0..fafef63 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -183,7 +183,7 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
-static inline unsigned __bio_segments(struct bio *bio, struct bvec_iter *bvec)
+static inline unsigned bio_segments(struct bio *bio)
 {
 	unsigned segs = 0;
 	struct bio_vec bv;
@@ -205,17 +205,12 @@ static inline unsigned __bio_segments(struct bio *bio, struct bvec_iter *bvec)
 		break;
 	}
 
-	__bio_for_each_segment(bv, bio, iter, *bvec)
+	bio_for_each_segment(bv, bio, iter)
 		segs++;
 
 	return segs;
 }
 
-static inline unsigned bio_segments(struct bio *bio)
-{
-	return __bio_segments(bio, &bio->bi_iter);
-}
-
 /*
  * get a reference to a bio, so it won't disappear. the intended use is
  * something like:
@@ -389,8 +384,6 @@ extern void bio_put(struct bio *);
 extern void __bio_clone_fast(struct bio *, struct bio *);
 extern struct bio *bio_clone_fast(struct bio *, gfp_t, struct bio_set *);
 extern struct bio *bio_clone_bioset(struct bio *, gfp_t, struct bio_set *bs);
-extern struct bio *bio_clone_bioset_partial(struct bio *, gfp_t,
-					    struct bio_set *, int, int);
 
 extern struct bio_set *fs_bio_set;