hikey: Use ro.serialno to set usb_gadget string am: 128d7e6340
am: 3bbda9524c

Change-Id: Icd832e0c227c5009198984eb842d2302d9727acd
diff --git a/init.hikey.usb.rc b/init.hikey.usb.rc
index 9ab3de3..de54dbd 100644
--- a/init.hikey.usb.rc
+++ b/init.hikey.usb.rc
@@ -7,7 +7,7 @@
     write /config/usb_gadget/g1/bcdDevice 0x0223
     write /config/usb_gadget/g1/bcdUSB 0x0200
     mkdir /config/usb_gadget/g1/strings/0x409 0770
-    write /config/usb_gadget/g1/strings/0x409/serialnumber "0123456789"
+    write /config/usb_gadget/g1/strings/0x409/serialnumber ${ro.serialno}
     write /config/usb_gadget/g1/strings/0x409/manufacturer "HISILICON"
     write /config/usb_gadget/g1/strings/0x409/product "ADB Gadget"
     mkdir /config/usb_gadget/g1/functions/accessory.gs2