KVM: VMX: add the __noclone attribute to vmx_vcpu_run

The changelog of 104f226b said "adds the __noclone attribute",
but it was missing in its patch. I think it is still needed.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>