ARM: dts: Enable support for USB 3.0 PHY controller for exynos5420

Add device tree nodes for USB 3.0 PHY present alongwith
USB 3.0 controller Exynos 5420 SoC. This phy driver is
based on generic phy framework.

Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>