mediatek: don't break auxadc without 32k clk

Make the newly added 32k clock optional for the auxadc driver also used
on pre-filogic platforms.

Signed-off-by: Daniel Golle <[email protected]>

target/linux/mediatek/patches-5.15/501-auxadc-add-auxadc-32k-clk.patch

@@ -8,14 +8,16 @@
  	struct mutex lock;
  	const struct mtk_auxadc_compatible *dev_comp;
  };
-@@ -222,6 +223,12 @@ static int __maybe_unused mt6577_auxadc_
+@@ -222,6 +223,14 @@ static int __maybe_unused mt6577_auxadc_
  		return ret;
  	}
  
-+	ret = clk_prepare_enable(adc_dev->adc_32k_clk);
-+	if (ret) {
-+		pr_err("failed to enable auxadc clock\n");
-+		return ret;
++	if (!IS_ERR(adc_dev->adc_32k_clk)) {
++		ret = clk_prepare_enable(adc_dev->adc_32k_clk);
++		if (ret) {
++			pr_err("failed to enable auxadc clock\n");
++			return ret;
++		}
 +	}
 +
  	mt6577_auxadc_mod_reg(adc_dev->reg_base + MT6577_AUXADC_MISC,