net: bridge: vlan: add rtm definitions and dump support

This patch adds vlan rtm definitions:
 - NEWVLAN: to be used for creating vlans, setting options and
   notifications
 - DELVLAN: to be used for deleting vlans
 - GETVLAN: used for dumping vlan information

Dumping vlans which can span multiple messages is added now with basic
information (vid and flags). We use nlmsg_parse() to validate the header
length in order to be able to extend the message with filtering
attributes later.

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

include/uapi/linux/rtnetlink.h

@@ -171,6 +171,13 @@ enum {
 	RTM_GETLINKPROP,
 #define RTM_GETLINKPROP	RTM_GETLINKPROP
 
+	RTM_NEWVLAN = 112,
+#define RTM_NEWNVLAN	RTM_NEWVLAN
+	RTM_DELVLAN,
+#define RTM_DELVLAN	RTM_DELVLAN
+	RTM_GETVLAN,
+#define RTM_GETVLAN	RTM_GETVLAN
+
 	__RTM_MAX,
 #define RTM_MAX		(((__RTM_MAX + 3) & ~3) - 1)
 };