usb: dwc2: Rename the dma_enable parameter to host_dma

Rename it so that it is more consistent with the gadget dma parameter.
It only affects host-mode operation so prefix it with "host".

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>