arm64: dts: renesas: Convert to new LVDS DT bindings

The internal LVDS encoder now has DT bindings separate from the DU. Port
the r8a7795 and r8a7796 device trees over to the new model.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>