USB: xhci: Add Makefile, MAINTAINERS, and Kconfig entries.

Add Makefile and Kconfig entries for the xHCI host controller driver.
List Sarah Sharp as the maintainer for the xHCI driver.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/Makefile b/drivers/usb/Makefile
index 0a3dc5e..19cb7d5 100644
--- a/drivers/usb/Makefile
+++ b/drivers/usb/Makefile
@@ -14,6 +14,7 @@
 obj-$(CONFIG_USB_OHCI_HCD)	+= host/
 obj-$(CONFIG_USB_UHCI_HCD)	+= host/
 obj-$(CONFIG_USB_FHCI_HCD)	+= host/
+obj-$(CONFIG_USB_XHCI_HCD)	+= host/
 obj-$(CONFIG_USB_SL811_HCD)	+= host/
 obj-$(CONFIG_USB_U132_HCD)	+= host/
 obj-$(CONFIG_USB_R8A66597_HCD)	+= host/