[ARM] 3753/1: S3C24XX: DMA fixes

Patch from Ben Dooks

A number of small issues with the S3C24XX DMA have
cropped up, which this patch fixes. These are:

  - check wether we can load another buff in start
  - update state handling in s3c2410_dma_lastxfer
  - only reload in irq if channel is not idle
  - more informative timeout errors (add source)
  - do not call request_irq() with irqs locked
  - added waitforstop function

The patch also adds a S3C2410_DMAOP_STARTED for
the occasions when the driver wants to ensure that
the DMA system load state is resynced after loading.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>