ASoC: amd: acp-es8336: use static variables

Sparse warnings:

sound/soc/amd/acp-es8336.c:36:15: error: symbol 'codec_dev' was not
declared. Should it be static?

sound/soc/amd/acp-es8336.c:37:18: error: symbol 'gpio_pa' was not
declared. Should it be static?
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220707214614.61081-1-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/amd/acp-es8336.c

@@ -33,8 +33,8 @@
 
 static unsigned long acp2x_machine_id;
 static struct snd_soc_jack st_jack;
-struct device *codec_dev;
-struct gpio_desc *gpio_pa;
+static struct device *codec_dev;
+static struct gpio_desc *gpio_pa;
 
 static int sof_es8316_speaker_power_event(struct snd_soc_dapm_widget *w,
 					  struct snd_kcontrol *kcontrol, int event)