media: media/cec.h: add CEC_CAP_DEFAULTS

The CEC_CAP_LOG_ADDRS, CEC_CAP_TRANSMIT, CEC_CAP_PASSTHROUGH and
CEC_CAP_RC capabilities are normally always present.

Add a CEC_CAP_DEFAULTS define that ORs these four caps to simplify
drivers.

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