net: phy: lxt: Add suspend/resume support to LXT971 and LXT973.

All LXT PHYs implement the standard "power down" bit 11 of
BMCR, so this patch adds support using the generic
genphy_{suspend,resume} functions added by
commit 0f0ca340e5 ("phy: power management support").

LXT970 is left aside because all registers get cleared upon
"power down" exit.

Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/lxt.c

@@ -262,6 +262,8 @@ static struct phy_driver lxt97x_driver[] = {
 	/* PHY_BASIC_FEATURES */
 	.ack_interrupt	= lxt971_ack_interrupt,
 	.config_intr	= lxt971_config_intr,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
 }, {
 	.phy_id		= 0x00137a10,
 	.name		= "LXT973-A2",
@@ -271,6 +273,8 @@ static struct phy_driver lxt97x_driver[] = {
 	.probe		= lxt973_probe,
 	.config_aneg	= lxt973_config_aneg,
 	.read_status	= lxt973a2_read_status,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
 }, {
 	.phy_id		= 0x00137a10,
 	.name		= "LXT973",
@@ -279,6 +283,8 @@ static struct phy_driver lxt97x_driver[] = {
 	.flags		= 0,
 	.probe		= lxt973_probe,
 	.config_aneg	= lxt973_config_aneg,
+	.suspend	= genphy_suspend,
+	.resume		= genphy_resume,
 } };
 
 module_phy_driver(lxt97x_driver);