ARM: S3C24XX: cleanup the included soc init functions in common.h

Only the _init, _init_clocks, _init_uarts and _map_io functions need
NULL defines, as they are used in the cpu map.

Further integrate the two restart functions already in common.h in
their respective soc part and compact the numerous empty lines.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>