netifd: refactor packet steering init

1. Move setup code to independent script file
2. Add init.d script to allow automatic updates
3. Support platform specific /usr/libexec/platform/packet-steering.sh

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

package/network/config/netifd/files/etc/init.d/packet_steering

@@ -0,0 +1,18 @@
+#!/bin/sh /etc/rc.common
+
+START=25
+USE_PROCD=1
+
+start_service() {
+	reload_service
+}
+
+service_triggers() {
+	procd_add_reload_trigger "network"
+	procd_add_reload_trigger "firewall"
+	procd_add_raw_trigger "interface.*" 1000 /etc/init.d/packet_steering reload
+}
+
+reload_service() {
+	/usr/libexec/network/packet-steering.sh
+}