RTL8393 SoCs older than Revision C hang on accesses to PHYs with PHY address
larger or equal to the CPU-port (52). This will make scanning the MDIO bus
hang forever. Since the RTL8390 platform does not support more than
52 PHYs, return -EIO for phy addresses >= 52. Note that the RTL8390 family
of SoCs has a fixed mapping between port number and PHY-address.
Signed-off-by: Birger Koblitz <git@birger-koblitz.de>
76f60470a1