USB: cdc-acm - blacklist IMS PCU device

The IMS PCU (Passenger Control Unit) device used custom protocol over serial
line, so it is presenting itself as CDC ACM device.

Now that we have proper in-kernel driver for it we need to black-list the
device in cdc-acm driver.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>