x86: ivybridge: Set up XHCI USB

Add init for XHCI so that high-speed USB can be used.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/ivybridge/Makefile b/arch/x86/cpu/ivybridge/Makefile
index 4a00757..aedc395 100644
--- a/arch/x86/cpu/ivybridge/Makefile
+++ b/arch/x86/cpu/ivybridge/Makefile
@@ -18,3 +18,4 @@
 obj-y += sata.o
 obj-y += sdram.o
 obj-y += usb_ehci.o
+obj-y += usb_xhci.o