drm/i915/fbc: replace a loop with drm_atomic_get_existing_crtc_state()

Much simpler. Thanks to Ville for pointing this.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1478883461-20201-3-git-send-email-paulo.r.zanoni@intel.com

drivers/gpu/drm/i915/intel_fbc.c

@@ -1071,7 +1071,7 @@ void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
 	struct drm_plane *plane;
 	struct drm_plane_state *plane_state;
 	bool fbc_crtc_present = false;
-	int i, j;
+	int i;
 
 	mutex_lock(&fbc->lock);
 
@@ -1092,23 +1092,20 @@ void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
 	for_each_plane_in_state(state, plane, plane_state, i) {
 		struct intel_plane_state *intel_plane_state =
 			to_intel_plane_state(plane_state);
+		struct intel_crtc_state *intel_crtc_state;
 
 		if (!intel_plane_state->base.visible)
 			continue;
 
 		if (!intel_fbc_can_choose(to_intel_crtc(plane_state->crtc)))
 			continue;
 
-		for_each_crtc_in_state(state, crtc, crtc_state, j) {
-			struct intel_crtc_state *intel_crtc_state =
-				to_intel_crtc_state(crtc_state);
-
-			if (plane_state->crtc != crtc)
-				continue;
+		intel_crtc_state = to_intel_crtc_state(
+			drm_atomic_get_existing_crtc_state(state,
+							   plane_state->crtc));
 
-			intel_crtc_state->enable_fbc = true;
-			goto out;
-		}
+		intel_crtc_state->enable_fbc = true;
+		break;
 	}
 
 out: