We should set ioeventfd_update_pending same as memory_region_update_pending.

Signed-off-by: linzhecheng <linzc@zju.edu.cn>
Message-Id: <1515934519-16158-1-git-send-email-linzc@zju.edu.cn>
Cc: qemu-stable@nongnu.org
Fixes: ade9c1aa
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>