ARM: dts: add exynos_usbphy node for exynos4

This patch enables a exynos_usbphy node for exynos4 SoCs.
A exynos4x12 usb phy node is almost same with 4210's one
except compatible string and pmu syscon.

Cc: Tomasz Figa <t.figa@samsung.com>
Cc: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>