net: airoha: Fix an error handling path in airoha_alloc_gdm_port()

If register_netdev() fails, the error handling path of the probe will not
free the memory allocated by the previous airoha_metadata_dst_alloc() call
because port->dev->reg_state will not be NETREG_REGISTERED.

So, an explicit airoha_metadata_dst_free() call is needed in this case to
avoid a memory leak.

Fixes: af3cf75 ("net: airoha: Move DSA tag in DMA descriptor")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1b94b91345017429ed653e2f05d25620dc2823f9.1746715755.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: tititiou36

drivers/net/ethernet/airoha/airoha_eth.c

@@ -2541,7 +2541,15 @@ static int airoha_alloc_gdm_port(struct airoha_eth *eth,
 	if (err)
 		return err;
 
-	return register_netdev(dev);
+	err = register_netdev(dev);
+	if (err)
+		goto free_metadata_dst;
+
+	return 0;
+
+free_metadata_dst:
+	airoha_metadata_dst_free(port);
+	return err;
 }
 
 static int airoha_probe(struct platform_device *pdev)