[ARM] 4155/1: S3C24XX: remove obj-dma-* from Makefile

In preperation for splitting the arch-s3c2410 directory
up, remove the use of obj-dma-y in the Makefile and move
to using CONFIG_S3C2440_DMA, CONFIG_S3C2412_DMA, etc.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>