Fix default_pdp_interface pointer reference

The default_pdp_interface was an array until
1352a3a26c4d7c32b38b7fadb837799a23014aa6 but is now a pointer
and should be used directly here.

Change-Id: I153802bddb2412f1b1d9e7a61081a5c6d34ee2cb
diff --git a/clatd.c b/clatd.c
index faeb679..d57ea59 100644
--- a/clatd.c
+++ b/clatd.c
@@ -75,7 +75,7 @@
   struct sockaddr_ll sll = {
     .sll_family   = AF_PACKET,
     .sll_protocol = htons(ETH_P_IPV6),
-    .sll_ifindex  = if_nametoindex((char *) &Global_Clatd_Config.default_pdp_interface),
+    .sll_ifindex  = if_nametoindex(Global_Clatd_Config.default_pdp_interface),
     .sll_pkttype  = PACKET_OTHERHOST,  // The 464xlat IPv6 address is not assigned to the kernel.
   };
   if (bind(sock, (struct sockaddr *) &sll, sizeof(sll))) {