stmmac: fix PHY reset during resume

When stmmac_mdio_reset, was called from stmmac_resume, it was not
resetting the PHY due to which MAC was not getting reset properly and
hence ethernet interface not was resumed properly.
The issue was currently only reproducible on stih301-b2204.

Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>