dt-bindings: spi: Add realtek,rtl9301-snand

Add a dtschema for the SPI-NAND controller on the RTL9300 SoCs. The
controller supports
 * Serial/Dual/Quad data with
 * PIO and DMA data read/write operation
 * Configurable flash access timing

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20241015225434.3970360-2-chris.packham@alliedtelesis.co.nz


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