net: phy: realtek: read actual speed on rtl8211f to detect downshift

The rtl8211f supports downshift and before commit 5502b218
("net: phy: use phy_resolve_aneg_linkmode in genphy_read_status")
the read-back of register MII_CTRL1000 was used to detect the
negotiated link speed.
The code added in commit d445dff2 ("net: phy: realtek: read
actual speed to detect downshift") is working fine also for this
phy and it's trivial re-using it to restore the downshift
detection on rtl8211f.

Add the phy specific read_status() pointing to the existing
function rtlgen_read_status().
Signed-off-by: Antonio Borneo <antonio.borneo@st.com>
Link: https://lore.kernel.org/r/478f871a-583d-01f1-9cc5-2eea56d8c2a7@huawei.comTested-by: Yonglong Liu <liuyonglong@huawei.com>
Link: https://lore.kernel.org/r/20201124230756.887925-1-antonio.borneo@st.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/realtek.c

@@ -729,6 +729,7 @@ static struct phy_driver realtek_drvs[] = {
 		PHY_ID_MATCH_EXACT(0x001cc916),
 		.name		= "RTL8211F Gigabit Ethernet",
 		.config_init	= &rtl8211f_config_init,
+		.read_status	= rtlgen_read_status,
 		.config_intr	= &rtl8211f_config_intr,
 		.handle_interrupt = rtl8211f_handle_interrupt,
 		.suspend	= genphy_suspend,