base-files: use "ports" array in board.json network for bridges

Bridge aggregates multiple ports so use a more accurate name ("ports")
and format (array) for storing them in board.json.

Example:

"network": {
	"lan": {
		"ports": [
			"lan1",
			"lan2",
			"lan3",
			"lan4"
		],
		"protocol": "static"
	},
	"wan": {
		"ifname": "wan",
		"protocol": "dhcp"
	}
}

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

package/base-files/files/lib/functions/uci-defaults.sh

@@ -39,7 +39,13 @@ ucidef_set_interface() {
 
 		[ -n "$opt" -a -n "$val" ] || break
 
-		json_add_string "$opt" "$val"
+		[ "$opt" = "ifname" -a "$val" != "${val/ //}" ] && {
+			json_select_array "ports"
+			for e in $val; do json_add_string "" "$e"; done
+			json_close_array
+		} || {
+			json_add_string "$opt" "$val"
+		}
 	done
 
 	if ! json_is_a protocol string; then