ASoC: siu: Add MODULE_FIRMWARE macro

The module loads firmware so add a MODULE_FIRMWARE macro to provide that
information via modinfo.

Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Link: https://lore.kernel.org/r/20230613095454.38696-1-juerg.haefliger@canonical.com


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