ARM: Kirkwood: Enable USB 3.0 in kirkwood_defconfig

Some QNAP devices has a USB 3.0 host controller on a PCIe bus.  Enable
the driver for this in the default configuration.
Reported-by: NMarek Vasut <marex@denx.de>
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/configs/kirkwood_defconfig

@@ -138,6 +138,7 @@ CONFIG_HID_TOPSEED=y
 CONFIG_HID_THRUSTMASTER=y
 CONFIG_HID_ZEROPLUS=y
 CONFIG_USB=y
+CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_EHCI_ROOT_HUB_TT=y
 CONFIG_USB_PRINTER=m