drm/sun4i: backend: Remove the MBUS quirks

Now that the MBUS quirks are applied by our global notifier, we can
remove them from our DRM driver.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/sun4i/sun4i_backend.c

@@ -805,25 +805,6 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
 		ret = of_dma_configure(drm->dev, dev->of_node, true);
 		if (ret)
 			return ret;
-	} else {
-		/*
-		 * If we don't have the interconnect property, most likely
-		 * because of an old DT, we need to set the DMA offset by hand
-		 * on our device since the RAM mapping is at 0 for the DMA bus,
-		 * unlike the CPU.
-		 *
-		 * XXX(hch): this has no business in a driver and needs to move
-		 * to the device tree.
-		 *
-		 * If we have two subsequent calls to dma_direct_set_offset
-		 * returns -EINVAL. Unfortunately, this happens when we have two
-		 * backends in the system, and will result in the driver
-		 * reporting an error while it has been setup properly before.
-		 * Ignore EINVAL, but it should really be removed eventually.
-		 */
-		ret = dma_direct_set_offset(drm->dev, PHYS_OFFSET, 0, SZ_4G);
-		if (ret && ret != -EINVAL)
-			return ret;
 	}
 
 	backend->engine.node = dev->of_node;