drivers: net: xgene: Add 10GbE support

- Added 10GbE support
- Removed unused macros/variables
- Moved mac_init call to the end of hardware init

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>