Properly set those bits to 1 that the spec demands in case bit 55 of
VMX_BASIC is 0 - like in our case.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>