USB: enclose USB_XHCI_HCD related symbols within a if USB_XHCI_HCD block

This patch encloses all symbols depending on USB_XHCI_HCD within an if
USB_XHCI_HCD / endif block.
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NFlorian Fainelli <florian@openwrt.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/Kconfig

@@ -25,13 +25,13 @@ config USB_XHCI_HCD
 	  To compile this driver as a module, choose M here: the
 	  module will be called xhci-hcd.
 
+if USB_XHCI_HCD
+
 config USB_XHCI_PLATFORM
 	tristate
-	depends on USB_XHCI_HCD
 
 config USB_XHCI_HCD_DEBUGGING
 	bool "Debugging for the xHCI host controller"
-	depends on USB_XHCI_HCD
 	---help---
 	  Say 'Y' to turn on debugging for the xHCI host controller driver.
 	  This will spew debugging output, even in interrupt context.
@@ -39,6 +39,8 @@ config USB_XHCI_HCD_DEBUGGING
 
 	  If unsure, say N.
 
+endif # USB_XHCI_HCD
+
 config USB_EHCI_HCD
 	tristate "EHCI HCD (USB 2.0) support"
 	depends on USB_ARCH_HAS_EHCI