pwm: lpss: Check PWM powerstate after resume on Cherry Trail devices

pwm: lpss: Check PWM powerstate after resume on Cherry Trail devices

The _PS0 method for the integrated graphics on some Cherry Trail devices
(observed on a HP Pavilion X2 10-p0XX) turns on the PWM chip (puts it in
D0), causing an inconsistency between the state the pm-core thinks it is
in (left runtime suspended as it was before the suspend/resume) and the
state it actually is in.

Interestingly enough this is done on a device where the pwm controller is
not used for the backlight at all, since it uses an eDP panel. On devices
where the PWM is used this is not a problem since we will resume it
ourselves anyways.

This inconsistency causes us to never suspend the pwm controller again,
which causes the device to not be able to reach S0ix states when suspended.

This commit adds a resume-complete handler, which when we think the device
is still run-time suspended checks the actual power-state and if necessary
updates the rpm-core's internal state.

This fixes the Pavilion X2 10-p0XX not reaching S0ix states when suspended.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>