The z_sched_cpu_usage() function was incorrectly using _current_cpu
instead of the requested cpu_id parameter when retrieving CPU usage
statistics. This caused it to always return stats from the current CPU
rather than the specified CPU.
This bug manifested in SMP systems when k_thread_runtime_stats_all_get()
looped through all CPUs - it would get stats from the wrong CPU for
each iteration, leading to inconsistent time values. For example, in
the times() POSIX function, this caused time to appear to move backwards:
t0: utime: 59908
t1: utime: 824
The fix ensures that:
1. cpu pointer is set to &_kernel.cpus[cpu_id] (the requested CPU)
2. The check for "is this the current CPU" is correctly written as
(cpu == _current_cpu)
This fixes the portability.posix.muti_process.newlib test failure
on FVP SMP platforms where times() was reporting backwards time.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
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