drm/i915: Use intel state as much as possible in wm code

Instead of directly referencing drm_crtc_state, convert to
intel_ctc_state and use the base struct. This is useful when we're
making the split between uapi and hw state, and also makes the
code slightly more readable.

A lot of places also use cstate, instead of the more common crtc_state.
Clean those up to use crtc_state. Same for pstate vs plane_state. (Ville)
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190628085517.31886-7-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -287,14 +287,14 @@ struct drm_i915_display_funcs {
 			  enum pipe pipe);
 	int (*get_fifo_size)(struct drm_i915_private *dev_priv,
 			     enum i9xx_plane_id i9xx_plane);
-	int (*compute_pipe_wm)(struct intel_crtc_state *cstate);
-	int (*compute_intermediate_wm)(struct intel_crtc_state *newstate);
+	int (*compute_pipe_wm)(struct intel_crtc_state *crtc_state);
+	int (*compute_intermediate_wm)(struct intel_crtc_state *crtc_state);
 	void (*initial_watermarks)(struct intel_atomic_state *state,
-				   struct intel_crtc_state *cstate);
+				   struct intel_crtc_state *crtc_state);
 	void (*atomic_update_watermarks)(struct intel_atomic_state *state,
-					 struct intel_crtc_state *cstate);
+					 struct intel_crtc_state *crtc_state);
 	void (*optimize_watermarks)(struct intel_atomic_state *state,
-				    struct intel_crtc_state *cstate);
+				    struct intel_crtc_state *crtc_state);
 	int (*compute_global_watermarks)(struct intel_atomic_state *state);
 	void (*update_wm)(struct intel_crtc *crtc);
 	int (*modeset_calc_cdclk)(struct intel_atomic_state *state);
@@ -1646,7 +1646,7 @@ struct drm_i915_private {
 		/*
 		 * Should be held around atomic WM register writing; also
 		 * protects * intel_crtc->wm.active and
-		 * cstate->wm.need_postvbl_update.
+		 * crtc_state->wm.need_postvbl_update.
 		 */
 		struct mutex wm_mutex;