netfilter: nft_flow_offload: fix underflow in flowtable reference counter

The .deactivate and .activate interfaces already deal with the reference
counter. Otherwise, this results in spurious "Device is busy" errors.

Fixes: a3c90f7a ("netfilter: nf_tables: flow offload expression")
Signed-off-by: Nwenxu <wenxu@ucloud.cn>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_flow_offload.c

@@ -200,9 +200,6 @@ static void nft_flow_offload_activate(const struct nft_ctx *ctx,
 static void nft_flow_offload_destroy(const struct nft_ctx *ctx,
 				     const struct nft_expr *expr)
 {
-	struct nft_flow_offload *priv = nft_expr_priv(expr);
-
-	priv->flowtable->use--;
 	nf_ct_netns_put(ctx->net, ctx->family);
 }