drm/i915: Create intel_dp->prepare_link_retrain() hook

In order to prepare for a link training with DDI, the state machine
would call intel_ddi_prepare_link_retrain(). To remove the dependency to
the hardware information, replace that direct call with a callback.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1445594525-7174-7-git-send-email-ander.conselvan.de.oliveira@intel.com
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index a721c50..87c786e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -802,6 +802,10 @@
 				     bool has_aux_irq,
 				     int send_bytes,
 				     uint32_t aux_clock_divider);
+
+	/* This is called before a link training is starterd */
+	void (*prepare_link_retrain)(struct intel_dp *intel_dp);
+
 	bool train_set_valid;
 
 	/* Displayport compliance testing */
@@ -1006,7 +1010,7 @@
 bool intel_ddi_pll_select(struct intel_crtc *crtc,
 			  struct intel_crtc_state *crtc_state);
 void intel_ddi_set_pipe_settings(struct drm_crtc *crtc);
-void intel_ddi_prepare_link_retrain(struct drm_encoder *encoder);
+void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp);
 bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector);
 void intel_ddi_fdi_disable(struct drm_crtc *crtc);
 void intel_ddi_get_config(struct intel_encoder *encoder,