eth1 is already assigned in many routers, use eth2 instead

[Hostle]

First off, great work. Your script helped answer a lot of the questions I faced while trying to tether the new iphones. I have a suggestion to improve the compatibility of the script to work with most if not all openwrt routers. In your script you test if eth1 is present if it's not then the usb interface is created and the script works perfect, however, if eth1 is present the the USB interface is not created. The limitation to this approach is that many devices already have an eth1 interface present, I suggest you use eth2 to prevent this. I have tested this on the gl-inet devices (eth1 is present in these devices) and it works great.