ARM: dts: s3c64xx: Use common macros for pinctrl configuration

Replace duplicated macros in each DTSI file with a common macro coming
from header.  Include the header in each pinctrl DTSI so further changes
could use it.

Although PIN_FUNC_SPC_2 does not bring much information about the
function itself, it still is more descriptive then hard-coded
number <2>.

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>