netfilter: nf_tables: fix percpu memory leak at nf_tables_addchain()

It seems to me that percpu memory for chain stats started leaking since
commit 3bc158f8 ("netfilter: nf_tables: map basechain priority to
hardware priority") when nft_chain_offload_priority() returned an error.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 3bc158f8 ("netfilter: nf_tables: map basechain priority to hardware priority")
Signed-off-by: Florian Westphal <fw@strlen.de>

net/netfilter/nf_tables_api.c

@@ -2243,6 +2243,7 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask,
 		if (err < 0) {
 			nft_chain_release_hook(&hook);
 			kfree(basechain);
+			free_percpu(stats);
 			return err;
 		}
 		if (stats)