mcastmngr: remove dependency on ports uci file

mcastmngr/files/common/etc/uci-defaults/61-mcast_config_generate

@@ -97,8 +97,7 @@ interfaces_ok(){
 		# mcast config is outdated, simply generate as per new logic
 		if [ -z "$dev_section" ]; then
 		       # check if the itf is a native interface	&& return 1
-			native=$(ubus call uci get '{"config":"ports", "type":"ethport", "match":{"ifname":"'"$itf"'"}}' | jsonfilter -e @.values | jq keys[])
-			[ -z "native" ] && return 1
+			[ -f "/proc/net/vlan/$itf" ] || return 1
 		fi
 	done
 	return 0