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: NPaul Zimmerman <paulz@synopsys.com>
Reviewed-by: NFelipe Balbi <balbi@ti.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>