geneve: implement support for IPv6-based tunnels

NOTE: Link-local IPv6 addresses for remote endpoints are not supported,
since the driver currently has no capacity for binding a geneve
interface to a specific link.
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Reviewed-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_link.h

@@ -461,6 +461,7 @@ enum {
 	IFLA_GENEVE_TOS,
 	IFLA_GENEVE_PORT,	/* destination port */
 	IFLA_GENEVE_COLLECT_METADATA,
+	IFLA_GENEVE_REMOTE6,
 	__IFLA_GENEVE_MAX
 };
 #define IFLA_GENEVE_MAX	(__IFLA_GENEVE_MAX - 1)