[RFT] net: fec: Fix MDIO polled IO

[Clemens Gruber]

Hi,

this patch fixes the problem on our i.MX6Q boards with Marvell 88E1510
PHYs (1000Base-T).

Tested-by: Clemens Gruber <clemens.gru...@pqgruber.com>

Thanks,
Clemens