ASoC: kirkwood: fix compilation warning in kirkwood_dma_open

writel() supposes the first argument of type unsigned int. This fix the
warning:

sound/soc/kirkwood/kirkwood-dma.c: In function 'kirkwood_dma_open':
sound/soc/kirkwood/kirkwood-dma.c:164:3: warning: large integer implicitly
truncated to unsigned type [-Woverflow]

Signed-off-by: Vladimir Murzin <murzin.v@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/sound/soc/kirkwood/kirkwood-dma.c b/sound/soc/kirkwood/kirkwood-dma.c
index 0c85c4e..55d0d9d3 100644
--- a/sound/soc/kirkwood/kirkwood-dma.c
+++ b/sound/soc/kirkwood/kirkwood-dma.c
@@ -159,7 +159,7 @@
 		 * Enable Error interrupts. We're only ack'ing them but
 		 * it's useful for diagnostics
 		 */
-		writel((unsigned long)-1, priv->io + KIRKWOOD_ERR_MASK);
+		writel((unsigned int)-1, priv->io + KIRKWOOD_ERR_MASK);
 	}
 
 	dram = mv_mbus_dram_info();