drm/i915: turn on the power well before suspending

Our suspend code touches a lot of registers all over the place, so we
need to enable the power well before suspending.

Signed-off-by: Paulo Zanoni <[e-mail]>
Reviewed-by: Jani Nikula <[e-mail]>
[danvet: Fixup compilation by stealing the header decl from the
dynamic power wells patch.]
Signed-off-by: Daniel Vetter <[e-mail]>

drivers/gpu/drm/i915/i915_drv.c

···
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	intel_set_power_well(dev, true);
+
 	drm_kms_helper_poll_disable(dev);
 
 	pci_save_state(dev->pdev);

drivers/gpu/drm/i915/intel_drv.h

···
 extern void intel_gpu_ips_teardown(void);
 
 extern void intel_init_power_well(struct drm_device *dev);
+extern void intel_set_power_well(struct drm_device *dev, bool enable);
 extern void intel_enable_gt_powersave(struct drm_device *dev);
 extern void intel_disable_gt_powersave(struct drm_device *dev);
 extern void gen6_gt_check_fifodbg(struct drm_i915_private *dev_priv);

drivers/gpu/drm/i915/intel_pm.c

···
 	dev_priv->display.init_clock_gating(dev);
 }
 
-static void intel_set_power_well(struct drm_device *dev, bool enable)
+void intel_set_power_well(struct drm_device *dev, bool enable)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	bool is_enabled, enable_requested;