hwrng: stm32 - use sizeof(*priv) instead of sizeof(struct stm32_rng_private)

Use sizeof(*priv) instead of sizeof(struct stm32_rng_private), the
former makes renaming of struct stm32_rng_private easier if necessary,
as it removes one site where such rename has to happen. No functional
change.
Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Uwe Kleine-König <ukleinek@kernel.org>
Acked-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/stm32-rng.c

@@ -517,7 +517,7 @@ static int stm32_rng_probe(struct platform_device *ofdev)
 	struct stm32_rng_private *priv;
 	struct resource *res;
 
-	priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;