selftests: kvm/x86: add test for pmu msr MSR_IA32_PERF_CAPABILITIES

This test will check the effect of various CPUID settings on the
MSR_IA32_PERF_CAPABILITIES MSR, check that whatever user space writes
with KVM_SET_MSR is _not_ modified from the guest and can be retrieved
with KVM_GET_MSR, and check that invalid LBR formats are rejected.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
Message-Id: <20210201051039.255478-12-like.xu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>