ARM: S3C24XX: Move S3C2440/S3C2442 plat-s3c24xx support to mach-s3c2440

Remove the old common S3C2440 and S3C2442 SoC support from plat-s3c24xx
into mach-s3c2440 now this directory is serving both SoCs.

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