perf stat: Don't size aggregation ids from user_requested_cpus

perf stat: Don't size aggregation ids from user_requested_cpus

As evsels may have additional CPU terms, the user_requested_cpus may
not reflect all the CPUs requested. Use evlist->all_cpus to size the
array as that reflects all the CPUs potentially needed by the evlist.

Reviewed-by: Thomas Falcon <thomas.falcon@intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20250719030517.1990983-4-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>