spi: airoha: add SPI-NAND Flash controller driver

Introduce support for SPI-NAND driver of the Airoha NAND Flash Interface
found on Airoha ARM SoCs.

Tested-by: Rajeev Kumar <Rajeev.Kumar@airoha.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/6c9db20505b01a66807995374f2af475a23ce5b2.1714377864.git.lorenzo@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>