ASoC: SOF: mediatek: add pcm_pointer callback for mt8186

add pcm_pointer callback for mt8186 to support read
host position from DSP

Signed-off-by: Chunxu Li <chunxu.li@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220921120239.31934-1-chunxu.li@mediatek.com


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