Revert "block: split bio if the only bvec's length is > SZ_4K"

We really don't need this, as the slow path will do the right thing
anyway.

This reverts commit 6952a7f8.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -320,7 +320,7 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio,
 		if (!q->limits.chunk_sectors &&
 		    (*bio)->bi_vcnt == 1 &&
 		    ((*bio)->bi_io_vec[0].bv_len +
-		     (*bio)->bi_io_vec[0].bv_offset) <= SZ_4K) {
+		     (*bio)->bi_io_vec[0].bv_offset) <= PAGE_SIZE) {
 			*nr_segs = 1;
 			break;
 		}