media: vivid: add <Vendor Command With ID> support

This makes it possible to test the new CEC_MSG_FL_REPLY_VENDOR_ID flag.

The vivid driver will Feature Abort any messages that do not have
exactly 1 payload byte. It ignores messages where the payload byte is
even, and where it is odd it will reply with the payload byte incremented
by 1. Basically a simple ping-pong command.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>