pm_suspend_via_firmware() will return false for platforms with ACPI
disabled and ACPI is a prerequisite for S0ix support.

With this patch, sleep state event sent to EC is forced to S3 if ACPI is
disabled.
Signed-off-by: NShawn Nematbakhsh <shawnn@chromium.org>
Signed-off-by: NThierry Escande <thierry.escande@collabora.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>