usb: Prefer firmware values when determining whether a port is removable

Windows appears to pay more attention to the ACPI values than any hub
configuration, so prefer the firmware's opinion on whether a port is
fixed or removable before falling back to the hub values.

Signed-off-by: Matthew Garrett <mjg59@coreos.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>