XGMAC supports following speeds:
	- 10G XGMII
	- 5G XGMII
	- 2.5G XGMII
	- 2.5G GMII
	- 1G GMII
	- 100M MII
	- 10M MII

Add them to the stmmac driver.
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>