ARM: dts: samsung: exynos5250-snow: use 'gpios' suffix for i2c-arb

Linux drivers support both variants - gpios and gpio - but first is
preferred.

Link: https://lore.kernel.org/r/20230721133246.15752-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>