The driver failed to take the dynamic ids into account when determining
the device type and therefore all devices were detected as 2-port
devices when using the dynamic-id interface.

Match on the usb-serial-driver field instead of doing redundant id-table
searches.
Reported-by: Anders Hammarquist <iko@iko.pp.se>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>