arm64: dts: mediatek: add mtk-snfi for mt7622

This patch adds a device-tree node for the MTK SPI-NAND Flash Interface
for MT7622 device tree.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
Link: https://lore.kernel.org/r/20220424032527.673605-6-gch981213@gmail.com


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