ACPI / idle: pass the cpuidle_device parameter

The cpuidle_device is retrieved in the function by using directly
the global variable. But the caller of this function already have
this device and it can be passed as a parameter. That is one small
step to encapsulate the code more.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Len Brown <len.brown@intel.com>