net: stmmac: Add support for SA Insertion/Replacement in XGMAC cores

Add the support for Source Address Insertion and Replacement in XGMAC
cores. Two methods are supported: Descriptor based and register based.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>