Add power button device in ACPI DSDT table.

Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Reviewed-by: Wei Huang <wei@redhat.com>
Tested-by: Wei Huang <wei@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Message-id: 1449804086-3464-6-git-send-email-zhaoshenglong@huawei.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>