With this patch the stmmac fails in case of the phy device
is not found; w/o this fix the mdio can be register twice when
do down/up the iface and this is not correct.
Reported-by: NStas <stsp@list.ru>
Signed-off-by: NGiuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>