drivers: net: xgene: Add second SGMII based 1G interface

- Added resource initialization based on port-id field
- Enabled second SGMII 1G interface

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