net: qmi_wwan: support devices having a shared QMI/wwan interface

Use the new cdc-wdm subdriver interface to create a device management
device even for USB devices having a single combined QMI/wwan USB
interface with three endpoints (int, bulk in, bulk out) instead of
separate data and control interfaces.

Some Huawei devices can be switched to a single interface mode for
use with other operating systems than Linux.  This adds support
for these devices when they run in such non-Linux modes.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>