usb: dwc3: add xHCI Host support

The Designware USB3 IP can be configured with
an internal xHCI. If we're running on such a
version, let's start the xHCI stack.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/Kconfig

@@ -2,6 +2,7 @@ config USB_DWC3
 	tristate "DesignWare USB3 DRD Core Support"
 	depends on (USB || USB_GADGET)
 	select USB_OTG_UTILS
+	select USB_XHCI_PLATFORM
 	help
 	  Say Y or M here if your system has a Dual Role SuperSpeed
 	  USB controller based on the DesignWare USB3 IP Core.