net: socionext: Fix error return code in netsec_netdev_open()

Fix to return error code -ENODEV from the of_phy_connect() error
handling case instead of 0, as done elsewhere in this function.

Fixes: 533dd11a ("net: socionext: Add Synquacer NetSec driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>