drm/i915: add intel_display_suspend, v2

This is a function used to disable all crtc's. This makes it clearer
to distinguish between when mode needs to be preserved and when
it can be trashed.

Changes since v1:
- Copy power changes from intel_crtc_control.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index a051a02..78ef0bb 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -601,7 +601,6 @@
 static int i915_drm_suspend(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct drm_crtc *crtc;
 	pci_power_t opregion_target_state;
 	int error;
 
@@ -632,8 +631,7 @@
 	 * for _thaw. Also, power gate the CRTC power wells.
 	 */
 	drm_modeset_lock_all(dev);
-	for_each_crtc(dev, crtc)
-		intel_crtc_control(crtc, false);
+	intel_display_suspend(dev);
 	drm_modeset_unlock_all(dev);
 
 	intel_dp_mst_suspend(dev);