gluon-wan-dnsmasq: use cellular DNS servers

Use DNS servers received from the cellular provider for the WAN dnsmasq
instance.

This fixes resolving VPN endpoint DNS requests when using only cellular
uplink.

Signed-off-by: David Bauer <mail@david-bauer.net>

package/gluon-wan-dnsmasq/files/etc/hotplug.d/iface/50-gluon-wan-dnsmasq

-if [ "$INTERFACE" = 'wan' -o "$INTERFACE" = 'wan6' ]; then
+if [ "$INTERFACE" = 'wan' -o "$INTERFACE" = 'wan6' -o "$INTERFACE" = 'cellular_4' -o "$INTERFACE" = 'cellular_6' ]; then
 	/lib/gluon/wan-dnsmasq/update.lua
 fi

package/gluon-wan-dnsmasq/files/lib/gluon/wan-dnsmasq/interface.d/050-gluon-wan-dnsmasq

 wan6
 wan
+cellular_4
+cellular_6