ARM: sa11x0: fix build errors from DMA engine API updates

The recent merge of the sa11x0 code into mainline had silent conflicts
with further development of the DMA engine API, leading to build errors
and warnings:

drivers/net/irda/sa1100_ir.c: In function 'sa1100_irda_dma_start':
drivers/net/irda/sa1100_ir.c:151: error: too few arguments to function 'chan->device->device_prep_slave_sg'
drivers/dma/sa11x0-dma.c: In function 'sa11x0_dma_probe':
drivers/dma/sa11x0-dma.c:950: warning: assignment from incompatible pointer type

Fix these.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/dma/sa11x0-dma.c b/drivers/dma/sa11x0-dma.c
index 16a6b48..ec78cce 100644
--- a/drivers/dma/sa11x0-dma.c
+++ b/drivers/dma/sa11x0-dma.c
@@ -585,7 +585,7 @@
 
 static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(
 	struct dma_chan *chan, struct scatterlist *sg, unsigned int sglen,
-	enum dma_transfer_direction dir, unsigned long flags)
+	enum dma_transfer_direction dir, unsigned long flags, void *context)
 {
 	struct sa11x0_dma_chan *c = to_sa11x0_dma_chan(chan);
 	struct sa11x0_dma_desc *txd;