net: marvell: prestera: Fix error return code in prestera_port_create()

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

Fixes: 501ef306

 ("net: marvell: prestera: Add driver for Prestera family ASIC devices")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Link: https://lore.kernel.org/r/1607071782-34006-1-git-send-email-zhangchangzhong@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>