net/8021q: Implement Multiple VLAN Registration Protocol (MVRP)

Initial implementation of the Multiple VLAN Registration Protocol
(MVRP) from IEEE 802.1Q-2011, based on the existing implementation
of the GARP VLAN Registration Protocol (GVRP).

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/uapi/linux/if_vlan.h

@@ -34,6 +34,7 @@ enum vlan_flags {
 	VLAN_FLAG_REORDER_HDR	= 0x1,
 	VLAN_FLAG_GVRP		= 0x2,
 	VLAN_FLAG_LOOSE_BINDING	= 0x4,
+	VLAN_FLAG_MVRP		= 0x8,
 };
 
 enum vlan_name_types {