Merge branch 'usb_cdc_fixes'

Bjørn Mork says:

====================
The 2 first patches in this series are required to make the Sierra
Wireless MC7710 card work in MBIM mode.  They may also be
required for other Qualcomm firmware based MBIM devices.

Patch #1 was previously posted as a standalone patch.  This version
is a replacement, removing a theoretical NULL pointer exception.

Patch #3 fixes a bug I introduced in v3.7
====================

Signed-off-by: David S. Miller <davem@davemloft.net>