drm/i915: Don't call intel_update_fbc from intel_crtc_cursor_set

Commit 74dff282 exposed this unnecessary call by causing a change in
the failure path on i965 where framebuffer compression will be turned
on and off on every cursor update. If you don't have the xf86-video-intel
fix to avoid the blinking cursor effect, this is very slow.

Symptoms were a far more noticeable cursor blink with every cursor image
change combined with severe slowdown for animated cursors.
Signed-off-by: NBrian Rogers <brian@xyzw.org>
Acked-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_display.c

@@ -3095,7 +3095,6 @@ static int intel_crtc_cursor_set(struct drm_crtc *crtc,
 	struct drm_gem_object *bo;
 	struct drm_i915_gem_object *obj_priv;
 	int pipe = intel_crtc->pipe;
-	int plane = intel_crtc->plane;
 	uint32_t control = (pipe == 0) ? CURACNTR : CURBCNTR;
 	uint32_t base = (pipe == 0) ? CURABASE : CURBBASE;
 	uint32_t temp = I915_READ(control);
@@ -3182,9 +3181,6 @@ static int intel_crtc_cursor_set(struct drm_crtc *crtc,
 		drm_gem_object_unreference(intel_crtc->cursor_bo);
 	}
 
-	if ((IS_I965G(dev) || plane == 0))
-		intel_update_fbc(crtc, &crtc->mode);
-
 	mutex_unlock(&dev->struct_mutex);
 
 	intel_crtc->cursor_addr = addr;