If selftest and reset are performed at the same time, the phy
loopback setting may be still in enable state after the reset,
and device cannot link up. So fix this issue by disabling phy
loopback before phy_start().

Fixes: 256727da ("net: hns3: Add MDIO support to HNS3 Ethernet driver for hip08 SoC")
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>