gpu: drm: vc4: simplify getting .drvdata

We should get drvdata from struct device directly. Going via
platform_device is an unneeded step back and forth.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180419140641.27926-17-wsa+renesas@sang-engineering.com

drivers/gpu/drm/vc4/vc4_drv.c

@@ -318,8 +318,7 @@ static int vc4_drm_bind(struct device *dev)
 
 static void vc4_drm_unbind(struct device *dev)
 {
-	struct platform_device *pdev = to_platform_device(dev);
-	struct drm_device *drm = platform_get_drvdata(pdev);
+	struct drm_device *drm = dev_get_drvdata(dev);
 
 	drm_dev_unregister(drm);