drivers: net: xgene: Preparing for adding SGMII based 1GbE

- Added link_state function pointer to the xgene__mac_ops structure
- Moved ring manager (pdata->rm) assignment to xgene_enet_setup_ops
- Removed unused variable (pdata->phy_addr) and macro (FULL_DUPLEX)

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>