drm_edid_to_eld: check for CEA data blocks only from structure revision 3 on

CEA datablocks are only defined from revision 3 onwards. Only check for
them if the revision says so.

Signed-of-by: Christian Schmidt <schmidt@digadd.de>
Tested-by: James Cloos <cloos@jhcloos.com>

Signed-off-by: Dave Airlie <airlied@redhat.com>