[media] cec: allow configuration both from within driver and from user space

It makes sense for adapters such as the Pulse-Eight to be configurable
both from within the driver and from user space, so remove the
requirement that drivers only can call cec_s_log_addrs or
cec_s_phys_addr if they don't expose those capabilities to user space.

Signed-off-by: Johan Fjeldtvedt <jaffe1@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>