USB: safe_serial: remove vendor/product module parameters

Remove the vendor and product module parameters which were added a long
time ago when we did not have the dynamic sysfs interface to add
new device ids (and which isn't limited to a single new vid/pid pair).

A vid/pid pair can be added dynamically using sysfs, for example:

  echo 04dd 1234 >/sys/bus/usb-serial/drivers/safe_serial/new_id

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>