net/phy: Add the autocross feature for forced links on VSC82x4

Add auto-MDI/MDI-X capability for forced (autonegotiation disabled)
10/100 Mbps speeds on Vitesse VSC82x4 PHYs. Exported previously static
function genphy_setup_forced() required by the new config_aneg handler
in the Vitesse PHY module.

Signed-off-by: Madalin Bucur <madalin.bucur@freescale.com>
Signed-off-by: Shruti Kanetkar <Shruti@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>