net/phy: micrel: Add workaround for bad autoneg

Very rarely, the KSZ9031 will appear to complete autonegotiation, but
will drop all traffic afterwards.  When this happens, the idle error
count will read 0xFF after autonegotiation completes.  Reset the PHY
when in that state.

Signed-off-by: Nathan Sullivan <nathan.sullivan@ni.com>
Signed-off-by: David S. Miller <davem@davemloft.net>