USB: serial: option: fix Telit Cinterion FE990A name

The correct name for FE990 is FE990A so use it in order to avoid
confusion with FE990B.

Cc: stable@vger.kernel.org
Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>