staging: HCD files for the DWC2 driver

These files contain the HCD code, and implement the Linux
hc_driver API. Support for both slave mode and buffer DMA mode
of the controller is included.

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