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/block/linux-aio.c b/block/linux-aio.c
index 16e09d1..d92513b 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -245,7 +245,7 @@
 
 BlockAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockDriverCompletionFunc *cb, void *opaque, int type)
+        BlockCompletionFunc *cb, void *opaque, int type)
 {
     struct qemu_laio_state *s = aio_ctx;
     struct qemu_laiocb *laiocb;