KVM: x86/pmu: Setup pmc->eventsel for fixed PMCs

The current pmc->eventsel for fixed counter is underutilised. The
pmc->eventsel can be setup for all known available fixed counters
since we have mapping between fixed pmc index and
the intel_arch_events array.

Either gp or fixed counter, it will simplify the later checks for
consistency between eventsel and perf_hw_id.

Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20211130074221.93635-2-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>