drm/i915: Read out the power sequencer port assignment on resume on vlv/chv

When we suspend we turn everything off so the pps should be idle, and we
also (or at least should) disable all power wells which will reset the
power sequencer port assignment. So when we resume all power sequencers
should be in their reset state. However it's at least theoretically
possible that the BIOS would touch the power seuqencer(s), so to be safe
we ought to read out the current port assignment like we do at driver
init time.

To do that we can simply call vlv_initial_power_sequencer_setup() from
the encoder ->reset() hook before calling intel_edp_panel_vdd_sanitize().
There's no danger or clobbering the pps delays since we now have those
stored within intel_dp and we don't change them once initialized.

This will make sure that the vdd state gets correctly tracked post-resume
in case the BIOS enabled it.

We need to shuffle things around a bit to get the locking right, and
while at it, make intel_edp_panel_vdd_sanitize() static and move it
around a bit to avoid a forward declaration.

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_drv.h

@@ -981,7 +981,6 @@ bool intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port,
 void intel_edp_backlight_on(struct intel_dp *intel_dp);
 void intel_edp_backlight_off(struct intel_dp *intel_dp);
 void intel_edp_panel_vdd_on(struct intel_dp *intel_dp);
-void intel_edp_panel_vdd_sanitize(struct intel_encoder *intel_encoder);
 void intel_edp_panel_on(struct intel_dp *intel_dp);
 void intel_edp_panel_off(struct intel_dp *intel_dp);
 void intel_edp_psr_enable(struct intel_dp *intel_dp);