EMAC driver: Fix bug: The clock divisor is set to all ones at reset.

Signed-off-by: Kalle Pokki <kalle.pokki@eke.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>