ARM: S3C64XX: Bypass legacy initialization when booting with DT

This patch allows bypassing most of legacy initialization when booting
an S3C64xx-based board using device tree, by adding conditional checks
for DT presence to initcalls which are no longer necessary when booting
with DT..

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