x86: ivybridge: Imply USB_XHCI_HCD

The Panther Point chipset connected to Ivybridge has xHC integrated,
imply it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/ivybridge/Kconfig

@@ -18,6 +18,7 @@ config NORTHBRIDGE_INTEL_IVYBRIDGE
 	imply SPI_FLASH
 	imply USB
 	imply USB_EHCI_HCD
+	imply USB_XHCI_HCD
 	imply VIDEO_VESA
 
 if NORTHBRIDGE_INTEL_IVYBRIDGE