ARM: dts: sun7i: Cubietruck: override regulator pin

Cubietruck uses different pin for the USB OTG VBUS that
is why we override the one defined in sunxi-common-regulators.dtsi

Signed-off-by: Roman Byshko <rbyshko@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>