KVM/x86: Use CC_SET()/CC_OUT in arch/x86/kvm/vmx.c

Remove open-coded uses of set instructions to use CC_SET()/CC_OUT() in
arch/x86/kvm/vmx.c.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
[Mark error paths as unlikely while touching this. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>