net: phy: add mdix_ctrl to hold the user configuration.

Add new parameter mdix_ctrl to hold the user configuration.
Existing mdix maintain the current status of MDI(X) crossover performed or
not.
mdix_ctrl can configure either ETH_TP_MDI or ETH_TP_MDI_X orETH_TP_MDI_AUTO.

Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microsemi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>