[media] media: doc-rst: document ENODATA for cropping ioctls

Document that the cropping ioctls can return ENODATA if the operation
isn't supported for the current input or output.

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