fix up yet more annoying signed/unsigned and mixed type errors
diff --git a/networking/udhcp/serverpacket.c b/networking/udhcp/serverpacket.c
index 1b89862..fe880b4 100644
--- a/networking/udhcp/serverpacket.c
+++ b/networking/udhcp/serverpacket.c
@@ -98,9 +98,9 @@
 {
 	packet->siaddr = server_config.siaddr;
 	if (server_config.sname)
-		strncpy(packet->sname, server_config.sname, sizeof(packet->sname) - 1);
+		strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
 	if (server_config.boot_file)
-		strncpy(packet->file, server_config.boot_file, sizeof(packet->file) - 1);
+		strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
 }