Refactor check_pmu_event_filter() in preparation for masked events.

No functional changes intended
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Link: https://lore.kernel.org/r/20221220161236.555143-4-aaronlewis@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>