btrfs: account that we're waiting for DIO read

Correctly account for IO when waiting for a submitted DIO read, the case
when we're retrying.  This only for the accounting purposes and should
not change other behaviour.

Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -8133,7 +8133,7 @@ next_block_or_try_again:
 			goto next;
 		}
 
-		wait_for_completion(&done.done);
+		wait_for_completion_io(&done.done);
 
 		if (!done.uptodate) {
 			/* We might have another mirror, so try again */
@@ -8247,7 +8247,7 @@ try_again:
 			goto next;
 		}
 
-		wait_for_completion(&done.done);
+		wait_for_completion_io(&done.done);
 
 		if (!done.uptodate) {
 			/* We might have another mirror, so try again */