net: phy: Fix modular PHYLIB build

net: phy: Fix modular PHYLIB build

After commit b87f211f3e38 ("net: Move PHY statistics code into PHY
library helpers") we made net/core/ethtool.c reference symbols which are
part of the library which can be modular. David introduced a temporary
fix with b914e1c0f562 ("phy: Temporary build fix after phylib changes.")
which would prevent such modularity.

This is not desireable of course, so instead, just inline the functions
into include/linux/phy.h to keep both options available.

Fixes: b87f211f3e38 ("net: Move PHY statistics code into PHY library helpers")
Fixes: b914e1c0f562 ("phy: Temporary build fix after phylib changes.")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>