ARM: dts: exynos: Use macros for pinctrl configuration on exynos3250

Usage of DTS macros instead of hard-coded numbers makes code easier to
read.  One does not have to remember which value means pull-up/down or
specific driver strength.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>