S3C: DMA: Change argument of s3c2410_dma_devconfig

All other functions have the channel argument of type 'unsigned int'
the s3c2410_dma_devconfig also accept the same value as argument but
treat it as type 'int'. Remove this anomaly by make it 'unsigned int'.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>