mrp: add periodictimer to allow retries when packets get lost

MRP doesn't implement the periodictimer in 802.1Q, so it never retries
if packets get lost.  I ran into this problem when MRP sent a MVRP
JoinIn before the interface was fully up.  The JoinIn was lost, MRP
didn't retry, and MVRP registration failed.

Tested against Juniper QFabric switches

Signed-off-by: Noel Burton-Krahn <noel@burton-krahn.com>
Acked-by: David Ward <david.ward@ll.mit.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/mrp.h b/include/net/mrp.h
index 4fbf02a..0f7558b 100644
--- a/include/net/mrp.h
+++ b/include/net/mrp.h
@@ -112,6 +112,7 @@
 	struct mrp_application	*app;
 	struct net_device	*dev;
 	struct timer_list	join_timer;
+	struct timer_list	periodic_timer;
 
 	spinlock_t		lock;
 	struct sk_buff_head	queue;