drm/v3d: Don't set drm_device->dev_private

And switch the helper over to container_of, which is a bunch faster
than chasing a pointer. Plus allows gcc to see through this maze.
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200415074034.175360-8-daniel.vetter@ffwll.ch

drivers/gpu/drm/v3d/v3d_drv.c

@@ -265,7 +265,6 @@ static int v3d_platform_drm_probe(struct platform_device *pdev)
 	}
 
 	platform_set_drvdata(pdev, drm);
-	drm->dev_private = v3d;
 	drmm_add_final_kfree(drm, v3d);
 
 	ret = map_regs(v3d, &v3d->hub_regs, "hub");

drivers/gpu/drm/v3d/v3d_drv.h

@@ -121,7 +121,7 @@ struct v3d_dev {
 static inline struct v3d_dev *
 to_v3d_dev(struct drm_device *dev)
 {
-	return (struct v3d_dev *)dev->dev_private;
+	return container_of(dev, struct v3d_dev, drm);
 }
 
 static inline bool