media: cec: clear all cec_log_addrs fields

The CEC version, vendor ID and OSD name were not cleared when clearing the
current set of logical addresses. This was unexpected and somewhat confusing,
so reset all these fields to their default values. Also document this since
the documentation wasn't quite clear either.

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