net: stmmac: selftests: Add tests for SA Insertion/Replacement

Add 4 new tests:
	- SA Insertion (register based)
	- SA Insertion (descriptor based)
	- SA Replacament (register based)
	- SA Replacement (descriptor based)

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