selftests/tc-testing: sfq: check that a derived limit of 1 is rejected

Because the limit is updated indirectly when other parameters are
updated, there are cases where even though the user requests a limit
of 2 it can actually be set to 1.

Add the following test cases to check that the kernel rejects them:
- limit 2 depth 1 flows 1
- limit 2 depth 1 divisor 1

Signed-off-by: Octavian Purdila <tavip@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>