[ARM] 4270/2: mach-s3c2443/irq.c off by one error in dma irqs

This patch corrects an error when demuxing the DMA irq's
DMA1 was used as a base and this should have been DMA0.
Without this fix we do not process DMA0 irq's and the
system effectively locks up in a loop trying the process
the irq it never can.

Signed-off-by: Graeme Gregory <gg@opensource.wolfsonmicro.com>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>