perf parse-events filter: Use evsel__find_pmu

Rather than manually scanning PMUs, use evsel__find_pmu that can use
the PMU set during event parsing.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250604174545.2853620-2-irogers@google.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>