ARM: dts: exynos: Use pinctrl labels in exynos4210-pinctrl

Labels for pinctrl's are defined in exynos4210.dtsi. Use them in
exynos4210-pinctrl instead of full names, as it is done in other Exynos
DTSes.

Signed-off-by: Maciej Purski <m.purski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>