selftests/tc-testing: add selftests for sfq qdisc

Test 7482: Create SFQ with default setting
Test c186: Create SFQ with limit setting
Test ae23: Create SFQ with perturb setting
Test a430: Create SFQ with quantum setting
Test 4539: Create SFQ with divisor setting
Test b089: Create SFQ with flows setting
Test 99a0: Create SFQ with depth setting
Test 7389: Create SFQ with headdrop setting
Test 6472: Create SFQ with redflowlimit setting
Test 8929: Show SFQ class

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>