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 <paulo.r.zanoni@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[danvet: Fixup compilation by stealing the header decl from the
dynamic power wells patch.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -470,6 +470,8 @@ static int i915_drm_freeze(struct drm_device *dev)
 {
 	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);