drm/nouveau/core: convert event handler apis to split create/enable semantics

This is a necessary step towards being able to work with the insane locking
requirements of the DRM core's vblank routines, and a nice cleanup as a
side-effect.

This is similar in spirit to the interfaces that Peter Hurley arrived at
with his nouveau_event rcu conversion series.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_display.h

@@ -36,6 +36,8 @@ struct nouveau_display {
 	int  (*init)(struct drm_device *);
 	void (*fini)(struct drm_device *);
 
+	struct nouveau_eventh **vblank;
+
 	struct drm_property *dithering_mode;
 	struct drm_property *dithering_depth;
 	struct drm_property *underscan_property;
@@ -59,6 +61,8 @@ void nouveau_display_fini(struct drm_device *dev);
 int  nouveau_display_suspend(struct drm_device *dev);
 void nouveau_display_repin(struct drm_device *dev);
 void nouveau_display_resume(struct drm_device *dev);
+int  nouveau_display_vblank_enable(struct drm_device *, int);
+void nouveau_display_vblank_disable(struct drm_device *, int);
 
 int  nouveau_crtc_page_flip(struct drm_crtc *crtc, struct drm_framebuffer *fb,
 			    struct drm_pending_vblank_event *event,