net: marvell: prestera: add missing unregister_netdev() in prestera_port_create()

If prestera_port_sfp_bind() fails, unregister_netdev() should be called
in error handling path.

Compile tested only.

Fixes: 52323ef7

 ("net: marvell: prestera: add phylink support")
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/1669115432-36841-1-git-send-email-zhangchangzhong@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>