Allow each CPU type in the S3C24XX range to
select the DMA channel mapping it supports.

We change the DMA registration to use an
virtual channel number that the DMA system
will allocate to a hardware channel at
request time.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>