drm: rcar-du: remove R-Car H3 ES1.* workarounds

R-Car H3 ES1.* was only available to an internal development group and
needed a lot of quirks and workarounds. These become a maintenance
burden now, so our development group decided to remove upstream support
for this SoC and prevent booting it. Public users only have ES2 onwards.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>