btrfs: fix an error handling path in btrfs_rename()

If new_whiteout_inode() fails, some resources need to be freed.
Add the missing goto to the error handling path.

Fixes: ab3c5c18 ("btrfs: setup qstr from dentrys using fscrypt helper")
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>