Revert "net: fec: Ensure clocks are enabled while using mdio bus"

This reverts commit 6c3e921b.

commit 6c3e921b ("net: fec: Ensure clocks are enabled while using mdio
 bus") prevents the kernel to boot on mx6 boards, so let's revert it.

Reported-by: Tyler Baker <tyler.baker@linaro.org>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>