staging: dwc2: when dma is disabled, clear hcd->self.uses_dma

When dma is disabled inside dwc2 (because the hardware does not support
it, or the code was changed to disable it for testing), let the usb core
know about this by clearing hcd->self.uses_dma.

By default, the usb core assumes that dma is used when a dma_mask is
set, but this might not always match the dma_enable value in dwc2. To
prevent problems resulting from a mismatch, better to explicitely
disable dma in this case (though everything seemed to work with the
wrong value of uses_dma as well, probably only resulted in some unneeded
work).

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>
Acked-by: Paul Zimmerman <Paul.Zimmerman@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>