net: ethernet: Add helper to determine if pause configuration is supported

Rather than have MAC drivers open code the test, add a helper in
phylib. This will help when we change the type of phydev->supported.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/dpaa/dpaa_ethtool.c

@@ -194,9 +194,7 @@ static int dpaa_set_pauseparam(struct net_device *net_dev,
 		return -ENODEV;
 	}
 
-	if (!(phydev->supported & SUPPORTED_Pause) ||
-	    (!(phydev->supported & SUPPORTED_Asym_Pause) &&
-	    (epause->rx_pause != epause->tx_pause)))
+	if (!phy_validate_pause(phydev, epause))
 		return -EINVAL;
 
 	/* The MAC should know how to handle PAUSE frame autonegotiation before