USB: QTI: Make changes to use QTI as transport with other USB functions

Currently USB QTI driver is used with USB RMNET function driver. This
change adds required support which allows to use QTI driver for control
transport with other USB function driver.

CRs-Fixed: 701879
Change-Id: Ia2991e615b4ef9a543d991c36e4de1de3539d3b0
Signed-off-by: Mayank Rana <mrana@codeaurora.org>