net/802: Implement Multiple Registration Protocol (MRP)

Initial implementation of the Multiple Registration Protocol (MRP)
from IEEE 802.1Q-2011, based on the existing implementation of the
Generic Attribute Registration Protocol (GARP).

Signed-off-by: David Ward <david.ward@ll.mit.edu>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1290,6 +1290,8 @@ struct net_device {
 	};
 	/* GARP */
 	struct garp_port __rcu	*garp_port;
+	/* MRP */
+	struct mrp_port __rcu	*mrp_port;
 
 	/* class/net/name entry */
 	struct device		dev;