perf test: Remove now unused subtest helpers

perf test: Remove now unused subtest helpers

Replaced by null terminated test case array.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Sohaib Mohamed <sohaib.amhmd@gmail.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20211104064208.3156807-16-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>