block: Rename BlockDriverCompletionFunc to BlockCompletionFunc

I'll use it with block backends shortly, and the name is going to fit
badly there.  It's a block layer thing anyway, not just a block driver
thing.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/dma-helpers.c b/dma-helpers.c
index 229192b..c347d4b 100644
--- a/dma-helpers.c
+++ b/dma-helpers.c
@@ -192,7 +192,7 @@
 
 BlockAIOCB *dma_bdrv_io(
     BlockDriverState *bs, QEMUSGList *sg, uint64_t sector_num,
-    DMAIOFunc *io_func, BlockDriverCompletionFunc *cb,
+    DMAIOFunc *io_func, BlockCompletionFunc *cb,
     void *opaque, DMADirection dir)
 {
     DMAAIOCB *dbs = qemu_aio_get(&dma_aiocb_info, bs, cb, opaque);