ASoC: ak5558: make two structures static

The structure ak5558_pm and soc_codec_dev_ak5558 are local to the
source and do not need to be in global scope, so make them static.
Also make soc_codec_dev_ak5558 static.

Cleans up sparse warnings:
warning: symbol 'ak5558_pm' was not declared. Should it be static?
warning: symbol 'soc_codec_dev_ak5558' was not declared. Should it be
static?
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/ak5558.c

@@ -322,13 +322,13 @@ static int __maybe_unused ak5558_runtime_resume(struct device *dev)
 	return regcache_sync(ak5558->regmap);
 }
 
-const struct dev_pm_ops ak5558_pm = {
+static const struct dev_pm_ops ak5558_pm = {
 	SET_RUNTIME_PM_OPS(ak5558_runtime_suspend, ak5558_runtime_resume, NULL)
 	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 				pm_runtime_force_resume)
 };
 
-struct snd_soc_component_driver soc_codec_dev_ak5558 = {
+static const struct snd_soc_component_driver soc_codec_dev_ak5558 = {
 	.probe			= ak5558_probe,
 	.remove			= ak5558_remove,
 	.controls		= ak5558_snd_controls,