fix found_type decrement in btrfs_truncate_in_trans

found_type has already been decreased by codes above the change,  I
think decrease it by one again doesn't make sense.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

fs/btrfs/inode.c

@@ -581,7 +581,7 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
 			} else {
 				break;
 			}
-			btrfs_set_key_type(&key, found_type - 1);
+			btrfs_set_key_type(&key, found_type);
 			continue;
 		}
 		if (btrfs_disk_key_offset(found_key) >= inode->i_size)