usb: dwc3: host: Change platform device ID for xhci-hcd to AUTO

Multiple dwc3 controllers will try to allocate multiple xhci-hcd
interfaces.
Changing platform device IDs from NONE to AUTO to support
such cases.

Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>