ASoC: dmaengine: Add missing module description

Now that make W=1 starts complaining the lack of MODULE_DESCRIPTION(),
let's add the missing information.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/ZjpQm-hxLQtpgkUx@smile.fi.intel.comSigned-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/20240508091909.27062-5-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-generic-dmaengine-pcm.c

@@ -494,4 +494,5 @@ void snd_dmaengine_pcm_unregister(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_unregister);
 
+MODULE_DESCRIPTION("ASoC helpers for generic PCM dmaengine API");
 MODULE_LICENSE("GPL");