drm/nouveau/tegra: Fix error pointer vs NULL return in nvkm_device_tegra_resource_addr()

The nvkm_device_tegra_resource() function returns a mix of error pointers
and NULL. The callers only expect it to return NULL on error. Change it
to only return NULL.

Fixes: 76b8f81a5b92 ("drm/nouveau: improve handling of 64-bit BARs")
Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Timur Tabi <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>
Link: https://lore.kernel.org/dri-devel/[e-mail]/T/#t

drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c

···
 	case NVKM_BAR1_FB : idx = 1; break;
 	default:
 		WARN_ON(1);
-		return ERR_PTR(-EINVAL);
+		return NULL;
 	}
 
 	return platform_get_resource(tdev->pdev, IORESOURCE_MEM, idx);