lldp: advertise system capabilities and the management address

Neighbours could not tell a bridge from a host and had no address to
reach us on. Add the System Capabilities TLV (bridge, enabled) and a
Management Address TLV with the IPv4 address, left out while the
address is still 0.0.0.0. Size the payload buffer for the frame it can
now hold: 64 bytes did not cover a 23 character hostname next to the
longer model names.

rtl837x_lldp.h

@@ -27,6 +27,18 @@
 #define LLDP_SYSNAME_TLV_TYPE 5
 #define LLDP_SYSDESC_TLV_TYPE 6
 
+#define LLDP_CAPABILITIES_TLV_TYPE 7
+#define LLDP_CAPABILITIES_TLV_LENGTH 4
+#define LLDP_CAPABILITY_BRIDGE 0x0004
+
+#define LLDP_MGMT_ADDR_TLV_TYPE 8
+#define LLDP_MGMT_ADDR_TLV_LENGTH 12
+#define LLDP_MGMT_ADDR_STR_LENGTH 5
+#define LLDP_MGMT_ADDR_SUBTYPE_IPV4 1
+#define LLDP_MGMT_IF_NUMBERING_UNKNOWN 1
+
+#define LLDP_MAX_PAYLOAD 128
+
 void lldp_init(void) __banked;
 void lldp_tick(void) __banked;
 void lldp_send(void) __banked;