[media] input: serio - add new protocol for the Pulse-Eight USB-CEC Adapter

This is for the new pulse8-cec staging driver.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>