net: sparx5: fix error return code in sparx5_register_notifier_blocks()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: d6fce514 ("net: sparx5: add switching support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>