Add a unified s3c24x0 header file

This patch adds a unified s3c24x0 cpu header file that selects the header
file for the specific s3c24x0 cpu from the SOC and CPU configs defined in
board config file. This removes the current chain of s3c24-type #ifdef's
from the s3c24x0 code.

Signed-off-by: Kevin Morfitt <kevin.morfitt@fearnside-systems.co.uk>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>