tc-testing: remove duplicate code in tdc.py

In set_operation_mode() function remove duplicated check for args.list
parameter, which is already done one line before.
Signed-off-by: Roman Mashak <mrv@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/tc-testing/tdc.py

@@ -712,7 +712,6 @@ def set_operation_mode(pm, parser, args, remaining):
         print_sll(ucat)
         exit(0)
 
-    if args.list:
     if args.list:
         list_test_cases(alltests)
         exit(0)