[media] pulse8-cec: new driver for the Pulse-Eight USB-CEC Adapter

This supports the Pulse-Eight USB-CEC Adapter.

It has been tested with firmware versions 4 and 5, but it should
hopefully work fine with older firmwares as well.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>