drm/i915: only set the intel_crtc DPMS mode to on if the mode set succeeded

If it failed, leave it in the "off" state.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/intel_display.c

@@ -5984,9 +5984,11 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 
 	ret = dev_priv->display.crtc_mode_set(crtc, mode, adjusted_mode,
 					      x, y, old_fb);
-
 	drm_vblank_post_modeset(dev, pipe);
 
+	if (ret)
+		intel_crtc->dpms_mode = DRM_MODE_DPMS_OFF;
+	else
 		intel_crtc->dpms_mode = DRM_MODE_DPMS_ON;
 
 	return ret;