ASoC: meson: aiu: make aiu_formatter_i2s_drv static

ASoC: meson: aiu: make aiu_formatter_i2s_drv static

aiu_formatter_i2s_drv is indeed used only in the aiu and it is not meant
to be exported. It should be static.

Cc: Valerio Setti <vsetti@baylibre.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202608080634.hf6aJGPB-lkp@intel.com/
Fixes: 83b83024cdbf ("ASoC: meson: aiu: use aiu-formatter-i2s to format I2S output data")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Valerio Setti <vsetti@baylibre.com>
Link: https://patch.msgid.link/20260812-aiu-formatter-static-v1-1-67936d57ba05@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>