Include support for Micrel KSZ9031 PHY driver in sunxi_defconfig,
which fixes issues of link not coming up at boot time with
certain link partners.

Micrel KSZ9031 PHY chip is used on Olimex A20-OLinuXino-LIME2
boards.

The errata fix itself has been implemented in commit
"3aed3e2a: net: phy: micrel: add Asym Pause workaround"
Signed-off-by: Priit Laes <plaes@plaes.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>