ASoC: rt5659: Use the devm_clk_get_optional() helper

Use devm_clk_get_optional() instead of hand writing it.
This saves some LoC and improves the semantic.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/5b44b2fddd8973e949e4ae2132971b147cfd1ec1.1684594544.git.christophe.jaillet@wanadoo.frSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5659.c

@@ -4141,13 +4141,9 @@ static int rt5659_i2c_probe(struct i2c_client *i2c)
 	regmap_write(rt5659->regmap, RT5659_RESET, 0);
 
 	/* Check if MCLK provided */
-	rt5659->mclk = devm_clk_get(&i2c->dev, "mclk");
-	if (IS_ERR(rt5659->mclk)) {
-		if (PTR_ERR(rt5659->mclk) != -ENOENT)
-			return PTR_ERR(rt5659->mclk);
-		/* Otherwise mark the mclk pointer to NULL */
-		rt5659->mclk = NULL;
-	}
+	rt5659->mclk = devm_clk_get_optional(&i2c->dev, "mclk");
+	if (IS_ERR(rt5659->mclk))
+		return PTR_ERR(rt5659->mclk);
 
 	rt5659_calibrate(rt5659);