perf test: Add asm pureloop test tool

Add test tool to be driven by further test scripts. This tool is pure
arm64 ASM with no libc usage to ensure it is the same exact binary/code
every time so it can also be re-used for many uses. It just loops for a
given fixed number of loops.

Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Carsten Haitzler <carsten.haitzler@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: coresight@lists.linaro.org
Link: https://lore.kernel.org/r/20220909152803.2317006-4-carsten.haitzler@foss.arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>