new helper: iov_iter_bvec()

similar to iov_iter_kvec(), for ITER_BVEC ones

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/splice.c b/fs/splice.c
index 75c6058..7c7176f 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1006,11 +1006,8 @@
 		}
 
 		/* ... iov_iter */
-		from.type = ITER_BVEC | WRITE;
-		from.bvec = array;
-		from.nr_segs = n;
-		from.count = sd.total_len - left;
-		from.iov_offset = 0;
+		iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
+			      sd.total_len - left);
 
 		/* ... and iocb */
 		init_sync_kiocb(&kiocb, out);