ASoC: codecs: rt5640: Simplify mclk initialization

Most of clk_xxx() functions do check if provided clk-pointer is
non-NULL. These do not check if the pointer is an error-pointer.
Providing such to a clk_xxx() results in a panic.

rt5640_set_dai_sysclk() is an example of that - clk_set_rate() is not
guarded by IS_ERR().

By utilizing _optional() variant of devm_clk_get() the driver code is
both simplified and more robust. There is no need to remember about
IS_ERR(clk) checks each time mclk is accessed.
Reviewed-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://msgid.link/r/20240221152516.852353-6-cezary.rojewski@intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5640.c

@@ -1949,9 +1949,6 @@ static int rt5640_set_bias_level(struct snd_soc_component *component,
 		 * away from ON. Disable the clock in that case, otherwise
 		 * enable it.
 		 */
-		if (IS_ERR(rt5640->mclk))
-			break;
-
 		if (snd_soc_component_get_bias_level(component) == SND_SOC_BIAS_ON) {
 			clk_disable_unprepare(rt5640->mclk);
 		} else {
@@ -2661,9 +2658,9 @@ static int rt5640_probe(struct snd_soc_component *component)
 	u32 val;
 
 	/* Check if MCLK provided */
-	rt5640->mclk = devm_clk_get(component->dev, "mclk");
-	if (PTR_ERR(rt5640->mclk) == -EPROBE_DEFER)
-		return -EPROBE_DEFER;
+	rt5640->mclk = devm_clk_get_optional(component->dev, "mclk");
+	if (IS_ERR(rt5640->mclk))
+		return PTR_ERR(rt5640->mclk);
 
 	rt5640->component = component;