media: vivid: fix disappearing <Vendor Command With ID> messages

The vivid driver supports the <Vendor Command With ID> message,
but if the Vendor ID of the received message didn't match the Vendor ID
of the CEC Adapter, then it ignores it (good) and returns 0 (bad).

It should return -ENOMSG to indicate that other followers should be
asked to handle it. Return code 0 means that the driver handled it,
which is wrong in this case.

As a result, userspace followers never get the chance to process such a
message.

Refactor the code a bit to have the function return -ENOMSG at the end,
drop the default case, and ensure that the message handlers return 0.

That way 0 is only returned if the message is actually handled in the
vivid_received() function.

Fixes: 812765cd ("media: vivid: add <Vendor Command With ID> support")
Cc: stable@vger.kernel.org
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>