ARM: dts: Add usb3503 pinctrl to exynos5250-spring

Reported-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Andreas Faerber <afaerber@suse.de>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>