bridge: Add netlink support for vlan_protocol attribute

This enables bridge vlan_protocol to be configured through netlink.

When CONFIG_BRIDGE_VLAN_FILTERING is disabled, kernel behaves the
same way as this feature is not implemented.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_link.h

@@ -231,6 +231,7 @@ enum {
 	IFLA_BR_STP_STATE,
 	IFLA_BR_PRIORITY,
 	IFLA_BR_VLAN_FILTERING,
+	IFLA_BR_VLAN_PROTOCOL,
 	__IFLA_BR_MAX,
 };