amt: add mld report message handler

In the previous patch, igmp report handler was added.
That handler can be used for mld too.
So, it uses that common code to parse mld report message.
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/amt.h

@@ -349,6 +349,7 @@ struct amt_dev {
 
 #define AMT_TOS			0xc0
 #define AMT_IPHDR_OPTS		4
+#define AMT_IP6HDR_OPTS		8
 #define AMT_GC_INTERVAL		(30 * 1000)
 #define AMT_MAX_GROUP		32
 #define AMT_MAX_SOURCE		128