A number of Huawei 3G and LTE modems implement a CDC NCM function,
including the necessary functional descriptors, but using a non
standard interface layout and class/subclass/protocol codes.

These devices can be handled by this driver with only a minor
change to the probing logic, allowing a single combined control
and data interface.  This works because the devices
- include a CDC Union descriptor labelling the combined
  interface as both master and slave, and
- have an alternate setting #1 for the bulk endpoints on the
  combined interface.

The 3G/LTE network connection is managed by vendor specific AT
commands on a serial function in the same composite device.
Handling the managment function is out of the scope of this
driver.  It will be handled by an appropriate USB serial
driver.

Reported-and-Tested-by: Olof Ermis <olof.ermis@gmail.com>
Reported-and-Tested-by: Tommy Cheng <tommy7765@yahoo.com>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>