bpf: add test cases to bpf selftests to cover all access tests

Lets add test cases to cover really all possible direct packet
access tests for good/bad access cases so we keep tracking them.

Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Acked-by: John Fastabend <[email protected]>
Signed-off-by: David S. Miller <[email protected]>