jme: Prevent possible read re-order error

Adding read memory barrier in between flag reading and data reading of
receive descriptors. This prevents the data being read before hardware
complete writing informations.
Reported-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Guo-Fu Tseng <cooldavid@cooldavid.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/jme.c

@@ -989,6 +989,7 @@ jme_process_receive(struct jme_adapter *jme, int limit)
 			goto out;
 		--limit;
 
+		rmb();
 		desccnt = rxdesc->descwb.desccnt & RXWBDCNT_DCNT;
 
 		if (unlikely(desccnt > 1 ||