Use G60_INTF instead of hardcoding the interface number 0

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Release USB interface prior to resetting

On newer kernels, failing to release the interface via libusb causes an
error:

    usb 2-2: usbfs: interface 0 claimed by usbfs while 'g60cuse' sets config #1

and then g60cuse gets stuck in a loop.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>