build: switch to firewall4 by default

This commit replaces firewall aka firewall3 with its nftables based
successor firewall4.

Signed-off-by: Paul Spooren <mail@aparcar.org>

include/target.mk

@@ -54,10 +54,9 @@ DEFAULT_PACKAGES.nas:=\
 # For router targets
 DEFAULT_PACKAGES.router:=\
 	dnsmasq \
-	firewall \
-	ip6tables \
-	iptables \
-	kmod-ipt-offload \
+	firewall4 \
+	nftables \
+	kmod-nft-offload \
 	odhcp6c \
 	odhcpd-ipv6only \
 	ppp \