xhci: fix wrong port number reported when setting USB2.0 hardware LPM.

This patch fix wrong port number reported when trying to enable/disable
USB2.0 hardware LPM.

Signed-off-by: Lin Wang <lin.x.wang@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>