Use the wrapper functions for getting and setting the driver data using
platform_device instead of using dev_{get,set}_drvdata() with &pdev->dev,
so we can directly pass a struct platform_device.

Also, unnecessary dev_set_drvdata() is removed, because the driver core
clears the driver data to NULL after device_release or on probe failure.
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>