qmi-over-mbim branch review

[Dan Williams]

Aleksander,

Looks OK to me (both libqmi and libmbim parts) though of course some of
the error handling and TID stuff still has to be done.

Also, device_open_context_step() should probably return an error if
!MBIM_QMUX and the user passes QMI_DEVICE_OPEN_FLAGS_MBIM.  Otherwise
clients would have no indication that the libqmi they are working with
doesn't have MBIM support, right?

Dan