ARM: SAMSUNG: Move plat-s3c Kconfig entries to plat-samsung and plat-s3c24xx

Move the Kconfig entries from plat-s3c to plat-samsung and plat-s3c24xx
as necessary. The S3C_BOOT entries and the DMA configuration can go to
plat-samsung. The low-level UART configurations are currently S3C2XX
specific and can go to plat-s3c24xx.

Eliminating plat-s3c from the build process will be submitted seperately.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>