net: stmmac: dwmac-qcom-ethqos: Add support for 2.5G SGMII

Serdes phy needs to operate at 2500 mode for 2.5G speed and 1000
mode for 1G/100M/10M speed.
Added changes to configure serdes phy and mac based on link speed.
Changing serdes phy speed involves multiple register writes for
serdes block. To avoid redundant write operations only update serdes
phy when new speed is different.
For 2500 speed MAC PCS autoneg needs to disabled. Added changes to
disable MAC PCS autoneg if ANE parameter is not set.

Signed-off-by: Sneh Shah <quic_snehshah@quicinc.com>
Tested-by: Abhishek Chauhan <quic_abchauha@quicinc.com> # sa8775p-ride
Reviewed-by: Abhishek Chauhan <quic_abchauha@quicinc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>