ARM: dts: exynos: Add new SoC specific compatible string for Exynos3250 SoC

Exynos3250 and Exynos5420 are using same compatible string for MFC codec
device but they have different clock hierarchy and complexity.  Add new
compatible string followed by mfc-v7 fallback for Exynos3250 SoC.

Suggested-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Aakarsh Jain <aakarsh.jain@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
Link: https://lore.kernel.org/r/20221114115024.69591-4-aakarsh.jain@samsung.com
Link: https://lore.kernel.org/r/20221116093010.18515-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Arnd Bergmann <arnd@arndb.de>