net: hns3: add set_loopback interface to realtek phy driver

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

When using Ubuntu OS, the realtek phy driver is loaded by default
instead of the generic PHY driver. However, the set_loopback
interface is not added to the realtek phy driver. As a result,
the phy selftest fails.

This patch adds the set_loopback interface to the realtek phy driver
so that the phy selftest can run properly.
Signed-off-by: NYufeng Mo <moyufeng@huawei.com>
Reviewed-by: Nlipeng <lipeng321@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/phy/realtek.c

@@ -291,6 +291,7 @@ static struct phy_driver realtek_drvs[] = {
 		.resume		= genphy_resume,
 		.read_page	= rtl821x_read_page,
 		.write_page	= rtl821x_write_page,
+		.set_loopback   = genphy_loopback,
 	}, {
 		.phy_id		= 0x001cc961,
 		.name		= "RTL8366RB Gigabit Ethernet",