net: phy: report link partner features through ethtool

The PHY library already reads the MII_STAT1000 and MII_LPA registers in
genphy_read_status(), so extend it to also populate the PHY device link
partner advertised features such that we can feed this back into ethtool
when asked for it in phy_ethtool_gset().

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/phy.h

@@ -287,8 +287,8 @@ struct phy_c45_device_ids {
  * adjust_state: Callback for the enet driver to respond to
  * changes in the state machine.
  *
- * speed, duplex, pause, supported, advertising, and
- * autoneg are used like in mii_if_info
+ * speed, duplex, pause, supported, advertising, lp_advertising,
+ * and autoneg are used like in mii_if_info
  *
  * interrupts currently only supports enabled or disabled,
  * but could be changed in the future to support enabling
@@ -340,6 +340,7 @@ struct phy_device {
 	/* See mii.h for more info */
 	u32 supported;
 	u32 advertising;
+	u32 lp_advertising;
 
 	int autoneg;