bridge: mcast: use names for the different multicast_router types

Using raw values makes it difficult to extend and also understand the
code, give them names and do explicit per-option manipulation in
br_multicast_set_port_router.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_bridge.h

@@ -177,6 +177,13 @@ enum {
 };
 #define MDBA_MDB_EATTR_MAX (__MDBA_MDB_EATTR_MAX - 1)
 
+/* multicast router types */
+enum {
+	MDB_RTR_TYPE_DISABLED,
+	MDB_RTR_TYPE_TEMP_QUERY,
+	MDB_RTR_TYPE_PERM,
+};
+
 enum {
 	MDBA_ROUTER_UNSPEC,
 	MDBA_ROUTER_PORT,