[media] cec: add MEDIA_SUPPORT dependency

The MEDIA_CEC_EDID option is guarded by MEDIA_SUPPORT, so selecting
it from MEDIA_CEC produces a warning:

warning: (MEDIA_CEC) selects MEDIA_CEC_EDID which has unmet direct dependencies (MEDIA_SUPPORT)

The warning is harmless, but it's better to add an explicit
dependency to shut it up, to reduce the noise during randconfig
builds.

Fixes: ca684386

 ("[media] cec: add HDMI CEC framework (api)")

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