Add setup for ethernet on SMDKC100, allowing kernel/ramdisk to be
loaded over tftp.

The preinit function will configure GPIO (GPK0CON) & SROMC to look
for environment in SROM Bank 3.
Signed-off-by: NNaveen Krishna Ch <ch.naveen@samsung.com>
Signed-off-by: NMinkyu Kang <mk7.kang@samsung.com>