staging: HCD descriptor DMA support for the DWC2 driver

This file contains code to support the HCD descriptor DMA mode of
the controller

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>