MLK-9919 net: fec: reinit MAC0 MII bus for MAC1 use after resume back

i.MX6SX-AI board has two enet MACs (MAC0 and MAC1), they share MAC0 MII
bus. When PHY0 don't connect to enet MAC0, MAC0 mii bus probe phy0 failed,
and the net interface is set to unattach mode. During suspend resume test,
driver don't reinit MAC0 after resume back, so MII bus don't work that causes
MAC1 also cannot access PHY1.

The patch just is workaround that reinit MAC0 MII bus for MAC1 using.

Signed-off-by: Fugang Duan <B38611@freescale.com>