net/sched: fix refcnt leak in the error path of tcf_vlan_init()

Similarly to what was done with commit a52956df ("net sched actions:
fix refcnt leak in skbmod"), fix the error path of tcf_vlan_init() to avoid
refcnt leaks when wrong value of TCA_VLAN_PUSH_VLAN_PROTOCOL is given.

Fixes: 5026c9b1 ("net sched: vlan action fix late binding")
CC: Roman Mashak <mrv@mojatatu.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_vlan.c

@@ -161,6 +161,8 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
 			case htons(ETH_P_8021AD):
 				break;
 			default:
+				if (exists)
+					tcf_idr_release(*a, bind);
 				return -EPROTONOSUPPORT;
 			}
 		} else {