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>