net: phy: Fix modular PHYLIB build

After commit c59530d0d5 ("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 1ecd6e8ad9 ("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: c59530d0d5 ("net: Move PHY statistics code into PHY library helpers")
Fixes: 1ecd6e8ad9 ("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>

drivers/net/phy/Kconfig

@@ -9,6 +9,7 @@ menuconfig MDIO_DEVICE
 
 config MDIO_BUS
 	tristate
+	default m if PHYLIB=m
 	default MDIO_DEVICE
 	help
 	  This internal symbol is used for link time dependencies and it
@@ -170,7 +171,7 @@ config PHYLINK
 	  autonegotiation modes.
 
 menuconfig PHYLIB
-	bool "PHY Device support and infrastructure"
+	tristate "PHY Device support and infrastructure"
 	depends on NETDEVICES
 	select MDIO_DEVICE
 	help