This lets userspace read the MSR_IA32_ARCH_CAPABILITIES and check that all
requested features are available on the host.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

CVE-2018-3620
CVE-2018-3646

(backported from commit cd283252)
[tyhicks: Adjust for the missing MSR_F10H_DECFG and MSR_IA32_UCODE_REV
 feature MSRs which do not exist in 4.15]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>