ARM: dts: exynos: correct SPI nor compatible in SMDK5250

SPI NOR flash compatible should come with generic jedec,spi-nor fallback
and proper vendor prefix:

  exynos5250-smdk5250.dtb: /soc/spi@12d30000/flash@0: failed to match any schema with compatible: ['w25x80']

Link: https://lore.kernel.org/r/20230208164942.387390-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>