usb: usb3 ports do not support FEAT_C_ENABLE

The port pm_runtime implementation unconditionally clears FEAT_C_ENABLE
after clearing PORT_POWER, but the bit is reserved on usb3 hub ports.
We expect khubd to be prevented from running because the port state is
not RPM_ACTIVE, so we need to clear any errors for usb2 ports.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/port.c

@@ -142,7 +142,8 @@ static int usb_port_runtime_suspend(struct device *dev)
 	set_bit(port1, hub->busy_bits);
 	retval = usb_hub_set_port_power(hdev, hub, port1, false);
 	usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
-	usb_clear_port_feature(hdev, port1,	USB_PORT_FEAT_C_ENABLE);
+	if (!port_dev->is_superspeed)
+		usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);
 	clear_bit(port1, hub->busy_bits);
 	usb_autopm_put_interface(intf);