s3c2410 and s3c2442 share the same dma channels while s3c2440 has
slight differences. But on all three the reachable sources per dma
channel has constraints attached and thus encodes the usable
combinations using the S3C24XX_DMA_CHANREQ macro.

This also fixes the warning about s3c2410_dma_resource being unused
as reported by Olof Johansson.
Reported-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>