drm/i915: Nuke legacy flip queueing code

Just a very minimal patch to nuke that code. Lots of the flip
interrupt handling stuff is still around.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170719125502.25696-2-daniel.vetter@ffwll.ch

drivers/gpu/drm/i915/i915_drv.h

@@ -715,11 +715,6 @@ struct drm_i915_display_funcs {
 	void (*fdi_link_train)(struct intel_crtc *crtc,
 			       const struct intel_crtc_state *crtc_state);
 	void (*init_clock_gating)(struct drm_i915_private *dev_priv);
-	int (*queue_flip)(struct drm_device *dev, struct drm_crtc *crtc,
-			  struct drm_framebuffer *fb,
-			  struct drm_i915_gem_object *obj,
-			  struct drm_i915_gem_request *req,
-			  uint32_t flags);
 	void (*hpd_irq_setup)(struct drm_i915_private *dev_priv);
 	/* clock updates for mode set */
 	/* cursor updates */