[media] cec: set unclaimed addresses to CEC_LOG_ADDR_INVALID

Up to 4 logical addresses can be claimed. Make sure that any
unclaimed logical addresses are set to CEC_LOG_ADDR_INVALID as
per the documentation.

Take special care in the unregistered case: when falling back to
unregistered num_log_addrs may be > 1, so mark those as invalid.

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