[media] cec: return -EPERM when no LAs are configured

The CEC_TRANSMIT ioctl now returns -EPERM if an attempt is made to
transmit a message for an unconfigured adapter (i.e. userspace
never called CEC_ADAP_S_LOG_ADDRS).

This differentiates this case from when LAs are configured, but no
physical address is set. In that case -ENONET is returned.

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