tests: latency_measure: Add busy threads for SMP

The latency_measure benchmark is designed for systems with a single
CPU. When the system allows for multiple CPUs, instead of forcing
a single CPU to be used via 'prj.conf', spawn a non-preemptible
thread to keep the other CPUs busy.

Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
2 files changed