ARM: dts: exynos: add USB DWC3 supplies to SMDK5250

Add required voltage regulators for USB DWC3 block on Exynos5250
SMDK5250 board.  Due to lack of board schematics, use same regulators as
on Arndale board.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20220123111644.25540-4-krzysztof.kozlowski@canonical.com