hwrng: tx4939 - remove unnecessary platform_set_drvdata()

The driver core clears the driver data to NULL after device_release
or on probe failure, since commit 0998d063
(device-core: Ensure drvdata = NULL when no driver is bound).
Thus, it is not needed to manually clear the device driver data to NULL.
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/tx4939-rng.c

@@ -154,7 +154,6 @@ static int __exit tx4939_rng_remove(struct platform_device *dev)
 	struct tx4939_rng *rngdev = platform_get_drvdata(dev);
 
 	hwrng_unregister(&rngdev->rng);
-	platform_set_drvdata(dev, NULL);
 	return 0;
 }