KVM does not let you read or write this MSR if the corresponding CPUID
bit is not set.  This in turn causes MSRs that come after MSR_TSC_AUX
to be ignored by KVM_SET_MSRS.

One visible symptom is that s3.flat from kvm-unit-tests fails with
CPUs that do not have RDTSCP, because the SMBASE is not reset to
0x30000 after reset.

Fixes: c9b8f6b6
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>