block: Remove obsolete BUG_ON

Now that bio_vecs are no longer cleared in bvec_alloc_bs() the following
BUG_ON must go.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
index 8396d74..549b014 100644
--- a/fs/bio-integrity.c
+++ b/fs/bio-integrity.c
@@ -140,7 +140,6 @@
 
 	iv = bip_vec_idx(bip, bip->bip_vcnt);
 	BUG_ON(iv == NULL);
-	BUG_ON(iv->bv_page != NULL);
 
 	iv->bv_page = page;
 	iv->bv_len = len;