KVM: arm64: selftests: get-reg-list: actually enable pmu regs in pmu sublist

We reworked get-reg-list to make it easier to enable optional register
sublists by parametrizing their vcpu feature flags as well as making
other generalizations. That was all to make sure we enable the PMU
registers when we want to test them. Somehow we forgot to actually
include the PMU feature flag in the PMU sublist description though!
Do that now.

Fixes: 313673ba

 ("KVM: arm64: selftests: get-reg-list: Split base and pmu registers")
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210713203742.29680-3-drjones@redhat.com