arm: socfpga: board: Repair Micrel PHY tuning

Add proper error checking into the PHY tuning patch. Make the PHY tunning only
happen in case the KSZ9021 PHY is enabled in config. Call the config callback
after the tuning finished.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@opensource.altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Tom Rini <trini@ti.com>
Cc: Pavel Machek <pavel@denx.de>