ARM: dts: Add USB host node for Exynos4

This patch adds EHCI and OHCI host device nodes for Exynos4.

Signed-off-by: Dongjin Kim <tobetter@gmail.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>