net: stmmac: socfpga: fix phy and ptp_ref setup for Arria10/Stratix10

On the Arria10, Agilex, and Stratix10 SoC, there are a few differences from
the Cyclone5 and Arria5:
 - The emac PHY setup bits are in separate registers.
 - The PTP reference clock select mask is different.
 - The register to enable the emac signal from FPGA is different.

Thus, this patch creates a separate function for setting the phy modes on
Arria10/Agilex/Stratix10. The separation is based a new DTS binding:
"altr,socfpga-stmmac-a10-s10".

Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>