drm/rcar-du: Don't set struct drm_device.irq_enabled

The field drm_device.irq_enabled is only used by legacy drivers
with userspace modesetting. Don't set it in rcar-du.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210625082222.3845-17-tzimmermann@suse.de

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -593,8 +593,6 @@ static int rcar_du_probe(struct platform_device *pdev)
 		goto error;
 	}
 
-	rcdu->ddev.irq_enabled = 1;
-
 	/*
 	 * Register the DRM device with the core and the connectors with
 	 * sysfs.