group: Add cdm-oemcrypto to the video group

On certain implementations, this user will need to open
/dev/dri/renderD128 which is owned by the video group.

BUG=b:153111783
TEST=None

Cq-Depend: chromium:2404105
Change-Id: I3c4ef83da730540024220dc5d221789eb585314b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/2369452
Tested-by: J Kardatzke <jkardatzke@chromium.org>
Tested-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Commit-Queue: Jeffrey Kardatzke <jkardatzke@google.com>