Whenever an MSR is part of KVM_GET_MSR_INDEX_LIST, as is the case for
MSR_K7_EVNTSEL0 or MSR_F15H_PERF_CTL0, it has to be always retrievable
and settable with KVM_GET_MSR and KVM_SET_MSR.

Accept a zero value for these MSRs to obey the contract.
Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20220601031925.59693-1-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>