xhci: don't dereference a xhci member after removing xhci

Remove the hcd after checking for the xhci last quirks, not before.

This caused a hang on a Alpine Ridge xhci based maching which remove
the whole xhci controller when unplugging the last usb device

CC: <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>