drm/renesas/rcar-du: Use fbdev-dma

drm/renesas/rcar-du: Use fbdev-dma

Implement fbdev emulation with fbdev-dma. Fbdev-dma now supports
damage handling, which is required by rcar-du. Avoids the overhead of
fbdev-generic's additional shadow buffering. No functional changes.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-29-tzimmermann@suse.de