drm/i915/vlv: T12 eDP panel timing enforcement during reboot

The panel power sequencer on vlv doesn't appear to accept changes to its
T12 power down duration during warm reboots. This change forces a delay
for warm reboots to the T12 panel timing as defined in the VBT table for
the connected panel.

Ver2: removed redundant pr_crit(), commented magic value for pp_div_reg

Ver3: moved SYS_RESTART check earlier, new name for pp_div.

Ver4: Minor issue changes

Ver5: Move registration of reboot notifier to edp_connector_init,
      Added warning comment to handler about lack of PM notification.

Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index eaa27ee..f67340e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -538,6 +538,8 @@
 	unsigned long last_power_on;
 	unsigned long last_backlight_off;
 	bool psr_setup_done;
+	struct notifier_block edp_notifier;
+
 	bool use_tps3;
 	struct intel_connector *attached_connector;