drm/nouveau: Use drm_crtc_vblank_off/on

With atomic nv50+ is already converted over to them, but the old
display code is still using it. Found in a 2 year old patch I have
lying around to un-export these old helpers!

v2: Drop the hand-rolled versions from resume/suspend code. Now that
crtc callbacks do this, we don't need a special case for s/r anymore.

v3: Remove unused variables.

v4: Don't remove drm_crtc_vblank_off from suspend paths, non-atomic
nouveau still needs that. But still switch to drm_crtc_vblank_off
since drm_vblank_off will disappear.

Cc: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161114114101.21731-1-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/nouveau/dispnv04/crtc.c b/drivers/gpu/drm/nouveau/dispnv04/crtc.c
index 0cb7a18..59d1d1c 100644
--- a/drivers/gpu/drm/nouveau/dispnv04/crtc.c
+++ b/drivers/gpu/drm/nouveau/dispnv04/crtc.c
@@ -702,7 +702,7 @@ static void nv_crtc_prepare(struct drm_crtc *crtc)
 	if (nv_two_heads(dev))
 		NVSetOwner(dev, nv_crtc->index);
 
-	drm_vblank_pre_modeset(dev, nv_crtc->index);
+	drm_crtc_vblank_off(crtc);
 	funcs->dpms(crtc, DRM_MODE_DPMS_OFF);
 
 	NVBlankScreen(dev, nv_crtc->index, true);
@@ -734,7 +734,7 @@ static void nv_crtc_commit(struct drm_crtc *crtc)
 #endif
 
 	funcs->dpms(crtc, DRM_MODE_DPMS_ON);
-	drm_vblank_post_modeset(dev, nv_crtc->index);
+	drm_crtc_vblank_on(crtc);
 }
 
 static void nv_crtc_destroy(struct drm_crtc *crtc)