trace/hwlat: Implement the per-cpu mode

Implements the per-cpu mode in which a sampling thread is created for
each cpu in the "cpus" (and tracing_mask).

The per-cpu mode has the potention to speed up the hwlat detection by
running on multiple CPUs at the same time, at the cost of higher cpu
usage with irqs disabled. Use with care.

[
  Changed get_cpu_data() to static.
  Reported-by: kernel test robot <[email protected]>
]

Link: https://lkml.kernel.org/r/ec06d0ab340e8460d293772faba19ad8a5c371aa.1624372313.git.bristot@redhat.com

Cc: Phil Auld <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Kate Carcia <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Alexandre Chartre <[email protected]>
Cc: Clark Willaims <[email protected]>
Cc: John Kacur <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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