KVM: x86: Mask off reserved bits in CPUID.80000001H

commit 0469e56a upstream.

KVM_GET_SUPPORTED_CPUID should only enumerate features that KVM
actually supports. CPUID.80000001:EBX[27:16] are reserved bits and
should be masked off.

Fixes: 07716717

 ("KVM: Enhance guest cpuid management")
Signed-off-by: Jim Mattson <jmattson@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>