libceph: record bio length

The bio is the only data item type that doesn't record its full
length.  Fix that.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index cb5b4e6..731bb9e 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -3032,6 +3032,7 @@
 	data = ceph_msg_data_create(CEPH_MSG_DATA_BIO);
 	BUG_ON(!data);
 	data->bio = bio;
+	data->bio_length = length;
 
 	msg->data = data;
 	msg->data_length = length;