ARM: dts: Split memory sections for exynos4210-origen

This patch changes memory configuration defined in dts file of Origen
board from single 1 GiB section into four 256 MiB sections to match
section size limit.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>