stable inclusion
from stable-5.10.8
commit 8d12c062ca995de6c3124d42d5d96c1ff9da4936
bugzilla: 47450

--------------------------------

[ Upstream commit f04bbcbf ]

When phy driver does not implement the set_loopback interface,
phy loopback test will return -EOPNOTSUPP, and the loopback test
will fail. So when phy driver does not implement the set_loopback
interface, don't do phy loopback test.

Fixes: c9765a89 ("net: hns3: add phy selftest function")
Signed-off-by: NYonglong Liu <liuyonglong@huawei.com>
Signed-off-by: NHuazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>