Fix a few Sparse warnings

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7016 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/dma-helpers.c b/dma-helpers.c
index 1469e34..f9eb224 100644
--- a/dma-helpers.c
+++ b/dma-helpers.c
@@ -81,7 +81,7 @@
     }
 }
 
-void dma_bdrv_cb(void *opaque, int ret)
+static void dma_bdrv_cb(void *opaque, int ret)
 {
     DMAAIOCB *dbs = (DMAAIOCB *)opaque;
     target_phys_addr_t cur_addr, cur_len;