perf test: Replace arm spe fork test workload with sqrtloop

perf test: Replace arm spe fork test workload with sqrtloop

So that it can get rid of requirement of a compiler.  I've also removed
killall as it'll kill perf process now and run the test workload for 10
sec instead.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: James Clark <james.clark@arm.com>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Zhengjun Xing <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20221116233854.1596378-9-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>