Three missing symbols were found during mpc85xx/p2020 compilation.
While at it, CONFIG_FSL_ENETC_MDIO is moved to generic config
for consistency.
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
[move CONFIG_FSL_ENETC_MDIO, remove redundant definitions, adjust
commit message/title]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>