arm64: dts: mt7986: add spi related device nodes

This patch adds spi support for MT7986.

Signed-off-by: Sam Shih <sam.shih@mediatek.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221118190126.100895-7-linux@fw-web.de


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>