The current option driver binds to the usb interface 2,3,4,5.
But the interface 4 and 5 doesn't answer to the AT commands.
On the new openwrt configuration the wwan script select the 5th
interface as control interface, failing to establish the
3G connection.
Backport the fix for the problem.
Signed-off-by: Giuseppe Lippolis <giu.lippolis@gmail.com>