target-i386: kvm_get/put_vcpu_events don't handle sipi_vector

qemu call kvm_get_vcpu_events, and kernel return sipi_vector always
0, never valid when reporting to user space. But when qemu calls
kvm_put_vcpu_events will make sipi_vector in kernel be 0. This will
accidently modify sipi_vector when sipi_vector in kernel is not 0.

Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
Reviewed-by: Liu Yi <liu.yi24@zte.com.cn>
Message-Id: <1500047256-8911-1-git-send-email-peng.hao2@zte.com.cn>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>