[libata] sata_dwc_460ex: signdness bug

dma_dwc_xfer_setup() returns an int and "dma_chan" needs to be signed
for the error handling to work.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index 2673a3d..6cf57c5 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
@@ -1459,7 +1459,7 @@
 {
 	struct scatterlist *sg = qc->sg;
 	struct ata_port *ap = qc->ap;
-	u32 dma_chan;
+	int dma_chan;
 	struct sata_dwc_device *hsdev = HSDEV_FROM_AP(ap);
 	struct sata_dwc_device_port *hsdevp = HSDEVP_FROM_AP(ap);
 	int err;