xhci: Handle clear PORT_POWER feature.

This patch makes the xHCI roothub code handle the clear PORT_POWER
feature request.  Setting port power is already handled.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>