net: Add link-local addressing support

Code based on networking/zcip.c in busybox
commit 8531d76a15890c2c535908ce888b2e2aed35b172

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/include/net.h b/include/net.h
index 52b9a29..a902a64 100644
--- a/include/net.h
+++ b/include/net.h
@@ -395,7 +395,7 @@
 
 enum proto_t {
 	BOOTP, RARP, ARP, TFTPGET, DHCP, PING, DNS, NFS, CDP, NETCONS, SNTP,
-	TFTPSRV, TFTPPUT
+	TFTPSRV, TFTPPUT, LINKLOCAL
 };
 
 /* from net/net.c */