can: at91_can: Fix memory leak in at91_can_probe()

In at91_can_probe(), the dev structure is allocated via alloc_candev().
However, if the subsequent call to devm_phy_optional_get() fails, the
code jumps directly to exit_iounmap, missing the call to free_candev().
This results in a memory leak of the allocated net_device structure.

Fix this by jumping to the exit_free label instead, which ensures that
free_candev() is called to properly release the memory.

Compile tested only. Issue found using a prototype static analysis tool
and code review.

Fixes: 3ecc09856afb ("can: at91_can: add CAN transceiver support")
Signed-off-by: Zilin Guan <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Marc Kleine-Budde <[e-mail]>

drivers/net/can/at91_can.c

···
 	if (IS_ERR(transceiver)) {
 		err = PTR_ERR(transceiver);
 		dev_err_probe(&pdev->dev, err, "failed to get phy\n");
-		goto exit_iounmap;
+		goto exit_free;
 	}
 
 	dev->netdev_ops	= &at91_netdev_ops;