btrfs: directly return 0 on no error code in btrfs_insert_raid_extent()

It's more obvious to return a literal zero instead of "return ret;".
Plus Smatch complains that ret could be uninitialized if the
ordered_extent->bioc_list list is empty and this silences that warning.
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/raid-stripe-tree.c

@@ -145,7 +145,7 @@ int btrfs_insert_raid_extent(struct btrfs_trans_handle *trans,
 		btrfs_put_bioc(bioc);
 	}
 
-	return ret;
+	return 0;
 }
 
 int btrfs_get_raid_extent_offset(struct btrfs_fs_info *fs_info,