drm/amdgpu: Use drm_crtc_vblank_on/off for dce6

This old code pattern was reintroduced in

Author: Ken Wang <Qingqing.Wang@amd.com>
Date:   Tue Jan 19 14:03:24 2016 +0800

    drm/amdgpu: add display controller implementation for si v10

Realign it with later display code. Tsk, tsk for massive copypasting
;-)

Cc: Christian König <christian.koenig@amd.com>
Cc: Ken Wang <Qingqing.Wang@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com> for the whole series.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161114090255.31595-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/amd/amdgpu/dce_v6_0.c

@@ -2040,13 +2040,13 @@ static void dce_v6_0_crtc_dpms(struct drm_crtc *crtc, int mode)
 		type = amdgpu_crtc_idx_to_irq_type(adev, amdgpu_crtc->crtc_id);
 		amdgpu_irq_update(adev, &adev->crtc_irq, type);
 		amdgpu_irq_update(adev, &adev->pageflip_irq, type);
-		drm_vblank_post_modeset(dev, amdgpu_crtc->crtc_id);
+		drm_crtc_vblank_on(crtc);
 		dce_v6_0_crtc_load_lut(crtc);
 		break;
 	case DRM_MODE_DPMS_STANDBY:
 	case DRM_MODE_DPMS_SUSPEND:
 	case DRM_MODE_DPMS_OFF:
-		drm_vblank_pre_modeset(dev, amdgpu_crtc->crtc_id);
+		drm_crtc_vblank_off(crtc);
 		if (amdgpu_crtc->enabled)
 			amdgpu_atombios_crtc_blank(crtc, ATOM_ENABLE);
 		amdgpu_atombios_crtc_enable(crtc, ATOM_DISABLE);