hwrng: stm32 - rename readl return value

Use a more meaningful name for the readl return value variable.

Link: https://lore.kernel.org/all/Y1J3QwynPFIlfrIv@loth.rohan.me.apana.org.au/Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/stm32-rng.c

@@ -49,13 +49,13 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 		/* Manage timeout which is based on timer and take */
 		/* care of initial delay time when enabling rng	*/
 		if (!sr && wait) {
-			int ret;
+			int err;
 
-			ret = readl_relaxed_poll_timeout_atomic(priv->base
+			err = readl_relaxed_poll_timeout_atomic(priv->base
 								   + RNG_SR,
 								   sr, sr,
 								   10, 50000);
-			if (ret)
+			if (err)
 				dev_err((struct device *)priv->rng.priv,
 					"%s: timeout %x!\n", __func__, sr);
 		}