ASoC: meson: Remove unused declartion in header file

The declaration of aiu_fifo_hw_free() has been removed since
commit e05cde84 ("ASoC: meson: Use managed DMA buffer allocation").
Let's remove the unused declaration.

Fixes: e05cde84 ("ASoC: meson: Use managed DMA buffer allocation")
Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://patch.msgid.link/20240910122330.70684-1-zhangzekun11@huawei.com


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