ARM: exynos: dts: Fixed vbus-gpios

The 'samsung,vbus-gpio' was submitted before pinmux landed for
exynos5250 and uses the old-style gpio specifier.  Fix the two
exynos5250 boards that use it.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>