[media] cec: drop MEDIA_CEC_DEBUG

Just depend on DEBUG_FS, no need to invent a new kernel config.
Especially since CEC can be enabled by drm without enabling
MEDIA_SUPPORT.

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