usb: rmnet: Allows other USB functions to use smd ctrl channel

Refactoring of rmnet ctrl channel over smd code to allow other
usb functions to re-use that code.

Change-Id: I1535f48a32acebe853f2bcc29a50d47fb9bc80b1
Signed-off-by: Bar Weiner <bweiner@codeaurora.org>
3 files changed