dt-bindings: Add vendor prefix for emtrion GmbH

emtrion is a system integrator and manufacturer of embedded systems.

Website: https://www.emtrion.de



Signed-off-by: Jan Tuerk <jan.tuerk@emtrion.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171123125600.41562-3-jan.tuerk@emtrion.com