ASoC: mediatek: mt6358: add missing EXPORT_SYMBOLs

Fixes the following build errors when mt6358 is configured as module:

>> ERROR: modpost: "mt6358_set_mtkaif_protocol"
>> [sound/soc/mediatek/mt8186/mt8186-mt6366-rt1019-rt5682s.ko] undefined!
>> ERROR: modpost: "mt6358_set_mtkaif_protocol"
>> [sound/soc/mediatek/mt8186/mt8186-mt6366-da7219-max98357.ko] undefined!

Fixes: 6a8d4198

 ("ASoC: mediatek: mt6358: add codec driver")
Signed-off-by: Jiaxin Yu <jiaxin.yu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220319120325.11882-1-jiaxin.yu@mediatek.com


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