KVM: VMX: Write VPID to vmcs when creating vcpu

Move the code that writes vmx->vpid to vmcs from vmx_vcpu_reset() to
vmx_vcpu_setup(), because vmx->vpid is allocated when creating vcpu and
never changed. So we don't need to update the vmcs.vpid when resetting
vcpu.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>