net: phy: mscc: Fix the VSC 8531/41 Chip Init sequence

- Turn on Broadcast writes
- UNH 1.8.1 clear bias for UNH 1000BT distortion
- UNH 1.8.7 optimize pre-emphasis for 100BasTx UNH 100W fix
- Enable Token-ring during 'Coma Mode'

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