tests: Remove unused options from tests.py

The test sub-command in tests.py incorrectly accepts various
formatting options in its usage string. These options aren't needed
since the test command doesn't produce any output.

Change-Id: I6d4731aa32a25a2286aa66548eaa0154a9392f79
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2840
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

tests/tests.py

@@ -280,8 +280,6 @@ def _test_args(subparsers):
         summary formatter, such a test would show up as 'CHANGED'.
         """)
 
-    _add_format_args(parser)
-
     parser.add_argument("result", type=argparse.FileType("rb"), nargs="*",
                         help="Pickled test results")