drivers: net: stmmac: add port selection programming

In case of SGMII more, for example when a MAC2MAC connection
is needed, the port selection bits (inside the MAC configuration
registers) have to be programmed according to the link selected.
So the patch adds a new DT parameter to pass the port selection
and to programmed related PCS and CORE to use it.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
index 51077a8..2533b91 100644
--- a/drivers/net/ethernet/stmicro/stmmac/common.h
+++ b/drivers/net/ethernet/stmicro/stmmac/common.h
@@ -531,6 +531,7 @@
 	unsigned int rx_csum;
 	unsigned int pcs;
 	unsigned int pmt;
+	unsigned int ps;
 };
 
 struct mac_device_info *dwmac1000_setup(void __iomem *ioaddr, int mcbins,