ASoC: doc: update codec example code

As the codec API has evolved the documentation has not kept up and still
uses old fields that have been removed.  Update the examples to
represent the current API.
Signed-off-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20211024151731.360638-1-john@metanate.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/sound/soc/codec.rst

@@ -40,7 +40,7 @@ e.g.
 	.prepare	= wm8731_pcm_prepare,
 	.hw_params	= wm8731_hw_params,
 	.shutdown	= wm8731_shutdown,
-	.digital_mute	= wm8731_mute,
+	.mute_stream	= wm8731_mute,
 	.set_sysclk	= wm8731_set_dai_sysclk,
 	.set_fmt	= wm8731_set_dai_fmt,
   };
@@ -60,7 +60,7 @@ e.g.
 		.rates = WM8731_RATES,
 		.formats = WM8731_FORMATS,},
 	.ops = &wm8731_dai_ops,
-	.symmetric_rates = 1,
+	.symmetric_rate = 1,
   };
 
 
@@ -177,10 +177,10 @@ when the mute is applied or freed.
 i.e.
 ::
 
-  static int wm8974_mute(struct snd_soc_dai *dai, int mute)
+  static int wm8974_mute(struct snd_soc_dai *dai, int mute, int direction)
   {
 	struct snd_soc_component *component = dai->component;
-	u16 mute_reg = snd_soc_component_read32(component, WM8974_DAC) & 0xffbf;
+	u16 mute_reg = snd_soc_component_read(component, WM8974_DAC) & 0xffbf;
 
 	if (mute)
 		snd_soc_component_write(component, WM8974_DAC, mute_reg | 0x40);