ASoC: xilinx: Add missing module descriptions

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.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/20240508091909.27062-8-tiwai@suse.de


Signed-off-by: Mark Brown <broonie@kernel.org>