The current S3C24XX DMA code does not allow for an peripheral
that has one channel for RX and another for TX.

This patch adds a per-cpu dma operation to select the transmit
or receive channel, and adds support to the S3C2412 for the
seperate DMA channels for TX and RX.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>