net: dhcp6: Send DHCPv6 using multicast MAC

In IPv6, the broadcast MAC address is not used.  Instead, it should use
the multicast address (see RFC RFC2464).

Add IPV6_ALL_NODE_ETH_ADDR macro for clarity.

Signed-off-by: Sean Edmond <seanedmond@microsoft.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/net/dhcpv6.h b/net/dhcpv6.h
index 65c8e4c..d41a3c3 100644
--- a/net/dhcpv6.h
+++ b/net/dhcpv6.h
@@ -40,7 +40,13 @@
 /* vendor-class-data to send in vendor clas option */
 #define DHCP6_VCI_STRING	"U-Boot"
 
-#define DHCP6_MULTICAST_ADDR	"ff02::1:2"	/* DHCP multicast address */
+/*
+ * All-DHCPv6 server multicast address
+ */
+#define DHCP6_MULTICAST_ADDR { { { 0xFF, 0x02, 0x00, 0x00, \
+								   0x00, 0x00, 0x00, 0x00, \
+								   0x00, 0x00, 0x00, 0x00, \
+								   0x00, 0x01, 0x00, 0x02 } } }
 
 /* DHCP6 States supported */
 enum dhcp6_state {