add xg521 gk7202v300+gc1054 with LTE modem (#15)

devices/gk7202v300_lite_xg521/general/overlay/etc/wireless/modem

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+set_gpio() {
+	[ "$2" -eq 1 ] && gpio set $1 || gpio clear $1
+	sleep 1
+}
+
+# GK7202V300 XG521 with EC800E and usb0
+if [ "$1" = "ec800e-gk7202v300-xg521" ]; then
+        set_gpio 9 0
+        modprobe usbserial vendor=0x2c7c product=0x0903
+        modprobe rndis_host
+        sleep 10
+        exit 0
+fi
+
+exit 1