spi/s3c64xx: Add the use of DMA config operation

Config operation is separated from request operation in
DMA common operation. Because spi driver can change the
DMA config for every transfer. So this patch is using the
separated DMA config operation.

Signed-off-by: Boojin Kim <boojin.kim@samsung.com>
Signed-off-by: Kyoungil Kim <ki0351.kim@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>