net: phy: Sort Makefile and Kconfig

Sort the files to reduce merge conflicts and to make it easier to find
drivers by name. Also separate the MDIO bus drivers from the PHY
drivers, again to help find what you need.

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