drm/i915/pmu: Only allow running on a single CPU

drm/i915/pmu: Only allow running on a single CPU

We do two things, both of which are purely to simplify and clarify the
implementation:

1.

Simplify the CPU online callback so it is more obvious that the purpose
there is to set a single CPU mask bit for the first CPU which comes
online. Using cpumask_weight for this reads more obvious than the trick
with cpumask_and_any.

2.

Modify the event init so that events can be created only on a single CPU.

This removes looking at the requested CPU thread siblings, and only allows
creating on the current active CPU.

Signed-off-by: Tvrtko Ursulin <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Dmitry Rogozhkin <[email protected]>
Tested-by: Chris Wilson <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]