[media] cec: Kconfig cleanup

The Kconfig options for the CEC subsystem were a bit messy. In
addition there were two cec sources (cec-edid.c and cec-notifier.c)
that were outside of the media/cec directory, which was weird.

Move those sources to media/cec as well.

The cec-edid and cec-notifier functionality is now part of the cec
module and these are no longer separate modules.

Also remove the MEDIA_CEC_EDID config option and include it with the
main CEC config option (which defined CEC_EDID anyway).

Added static inlines to cec-edid.h for dummy functions when CEC_CORE
isn't defined.

CEC drivers should now depend on CEC_CORE.

CEC drivers that need the cec-notifier functionality must explicitly
select CEC_NOTIFIER.

The s5p-cec and stih-cec drivers depended on VIDEO_DEV instead of
CEC_CORE, fix that as well.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>