net: stmmac: Add support for Enterprise MAC version

Adds the support for Enterprise MAC IP version which is very similar to
XGMAC. It's so similar that we just need to check the device id and add
new speeds definitions and some minor callbacks.

Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>