gnunet: depend on 'uci-firewall' instead of 'firewall'

To allow using gnunet on systems with firewall4, add replace direct
dependency on 'firewall' with 'uci-firewall' which is satisfied by
either 'firewall' or 'firewall4'.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

net/gnunet/Makefile

@@ -360,7 +360,7 @@ PLUGIN_fs-sqlite:=datastore_sqlite
 DEPENDS_utils:=+certtool +openssl-util
 BIN_utils:=gns-proxy-setup-ca transport-certificate-creation
 
-DEPENDS_vpn:=+kmod-tun +iptables +firewall
+DEPENDS_vpn:=+kmod-tun +iptables +uci-firewall
 BIN_vpn:=vpn
 FILE_MODES_vpn:=/usr/lib/gnunet/libexec/gnunet-helper-exit:root:gnunet:4750 /usr/lib/gnunet/libexec/gnunet-helper-vpn:root:gnunet:4750
 LIB_vpn:=dnsstub tun vpn