drm/shmobile: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()

As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() with DRM_MODESET_LOCK_ALL_BEGIN() and
DRM_MODESET_LOCK_ALL_END()
Signed-off-by: Fernando Ramos <greenfoo@u92.eu>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210924064324.229457-8-greenfoo@u92.eu

drivers/gpu/drm/shmobile/shmob_drm_drv.c

@@ -156,10 +156,12 @@ static int shmob_drm_pm_suspend(struct device *dev)
 static int shmob_drm_pm_resume(struct device *dev)
 {
 	struct shmob_drm_device *sdev = dev_get_drvdata(dev);
+	struct drm_modeset_acquire_ctx ctx;
+	int ret;
 
-	drm_modeset_lock_all(sdev->ddev);
+	DRM_MODESET_LOCK_ALL_BEGIN(sdev->ddev, ctx, 0, ret);
 	shmob_drm_crtc_resume(&sdev->crtc);
-	drm_modeset_unlock_all(sdev->ddev);
+	DRM_MODESET_LOCK_ALL_END(sdev->ddev, ctx, ret);
 
 	drm_kms_helper_poll_enable(sdev->ddev);
 	return 0;