net: stmmac: Add CBS support in XGMAC2

XGMAC2 uses the same CBS mechanism as GMAC5, only registers offset
changes. Lets use the same TC callbacks and implement the .config_cbs
callback in XGMAC2 core.

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