arm64: dts: mediatek: mt7986: fix SPI bus width properties

arm64: dts: mediatek: mt7986: fix SPI bus width properties

This fixes SPI setup and resolves following validation errors:
arch/arm64/boot/dts/mediatek/mt7986a-rfb.dtb: spi_nand@0: Unevaluated properties are not allowed ('spi-rx-buswidth', 'spi-tx-buswidth' were unexpected)
        from schema $id: http://devicetree.org/schemas/mtd/spi-nand.yaml#
arch/arm64/boot/dts/mediatek/mt7986b-rfb.dtb: spi_nand@0: Unevaluated properties are not allowed ('spi-rx-buswidth', 'spi-tx-buswidth' were unexpected)
        from schema $id: http://devicetree.org/schemas/mtd/spi-nand.yaml#

Fixes: 885e153ed7c1 ("arm64: dts: mt7986: add spi related device nodes")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20231116130952.5099-1-zajec5@gmail.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>