ARM: SAMSUNG: Don't export __init functions to modules

There are few functions marked as __init, but exported to modules in
devices declaration files.

s3c_nand_set_platdata() and s3c24xx_ts_set_platdata() are used only by
boards init code now, so remove EXPORT_SYMBOL() for them.

Signed-off-by: Yauhen Kharuzhy <jekhor@gmail.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>