udhcpc[6]: initialize entire sockaddr_ll

I see random field values like sll_hatype=0x267 when I strace.
They seem to not matter, but just in case they sometimes do,
let's at least have deterministic values (via memset(0)).

function                                             old     new   delta
change_listen_mode                                   308     322     +14

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/udhcp/d6_packet.c b/networking/udhcp/d6_packet.c
index 79a0ac8..a0656c1 100644
--- a/networking/udhcp/d6_packet.c
+++ b/networking/udhcp/d6_packet.c
@@ -75,6 +75,8 @@
 	dest_sll.sll_family = AF_PACKET;
 	dest_sll.sll_protocol = htons(ETH_P_IPV6);
 	dest_sll.sll_ifindex = ifindex;
+	/*dest_sll.sll_hatype = ARPHRD_???;*/
+	/*dest_sll.sll_pkttype = PACKET_???;*/
 	dest_sll.sll_halen = 6;
 	memcpy(dest_sll.sll_addr, dest_arp, 6);