net: phy: Uninline PHY ethtool statistics operations

Now that we have moved the PHY ethtool statistics to be dynamically
registered, we no longer need to inline those for ethtool. This used to
be done to avoid cross symbol referencing and allow ethtool to be
decoupled from PHYLIB entirely.

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