[media] cec-core.rst: document the new cec_get_drvdata() helper

Document the new cec_get_drvdata() helper function.

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