arm64: dts: exynos: Add regulators for Vbus and Vbus-Boost

Adding fixed voltage regulators for Vbus and Vbus-boost required
by USB 3.0 DRD controller on Exynos7-espresso board.

Signed-off-by: Vivek Gautam <gautamvivek1987@gmail.com>
Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>