spi: mtk-snfi: Add snfi support for MT7986 IC

Add snfi support for MT7986 IC.

Signed-off-by: Xiangsheng Hou <xiangsheng.hou@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221205065756.26875-2-xiangsheng.hou@mediatek.com


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