xhci: fix finding correct bus_state structure for USB 3.1 hosts

xhci driver keeps a bus_state structure for each hcd (usb2 and usb3)

The structure is picked based on hcd speed, but driver only compared
for HCD_USB3 speed, returning the wrong bus_state for HCD_USB31 hosts.

This caused null pointer dereference errors in bus_resume function.

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