usb: gadget: dwc3: Add support for DBM (MSM specific) endpoints.

In MSM architecture, the DBM, Device Bus Manager, is a HW module within
the USB3.0 core wrapper, implementing BAM interface support for USB3.0 IP.
The DBM HW unit requires for its operation a special transfer to be
started, with special TRBs structure. These usb requests will operate in
BAM2BAM mode.

This change adds to the dwc3-msm.c driver a support for queuing
a special transfers to endpoints which serve the DBM.

A function driver can now call to msm_ep_config(*ep) with some
endpoint which will serve the DBM. After this, the function
driver can queue a request to this endpoint as usual ep->queue(*ep,*req).
The function driver may need to add a few more parameters in req->udc_priv
field according to the bit mask fields defined in msm_hsudb.h file.

Change-Id: Iad530dabc68414c61d44e9eaef4402f868b2b12f
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>