KVM: arm64: pmu: Don't mark a counter as chained if the odd one is disabled

At the moment we update the chain bitmap on type setting. This
does not take into account the enable state of the odd register.

Let's make sure a counter is never considered as chained if
the high counter is disabled.

We recompute the chain state on enable/disable and type changes.

Also let create_perf_event() use the chain bitmap and not use
kvm_pmu_idx_has_chain_evtype().

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200124142535.29386-3-eric.auger@redhat.com