net: dsa: tag_8021q: avoid leaking ctx on dsa_tag_8021q_register() error path

If dsa_tag_8021q_setup() fails, for example due to the inability of the
device to install a VLAN, the tag_8021q context of the switch will leak.
Make sure it is freed on the error path.

Fixes: 328621f ("net: dsa: tag_8021q: absorb dsa_8021q_setup into dsa_tag_8021q_{,un}register")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20221209235242.480344-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: vladimiroltean

net/dsa/tag_8021q.c

@@ -398,6 +398,7 @@ static void dsa_tag_8021q_teardown(struct dsa_switch *ds)
 int dsa_tag_8021q_register(struct dsa_switch *ds, __be16 proto)
 {
 	struct dsa_8021q_context *ctx;
+	int err;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
@@ -410,7 +411,15 @@ int dsa_tag_8021q_register(struct dsa_switch *ds, __be16 proto)
 
 	ds->tag_8021q_ctx = ctx;
 
-	return dsa_tag_8021q_setup(ds);
+	err = dsa_tag_8021q_setup(ds);
+	if (err)
+		goto err_free;
+
+	return 0;
+
+err_free:
+	kfree(ctx);
+	return err;
 }
 EXPORT_SYMBOL_GPL(dsa_tag_8021q_register);