drm: Fix error handling in drm_mm eviction kselftest

        drivers/gpu/drm/selftests/test-drm_mm.c:1277 evict_everything()
        warn: calling list_del() inside list_for_each

The list_del() inside the error handling in the eviction loop is
overkill. We have to undo the eviction scan to return the drm_mm back to
a recoverable state, so have to iterate over the full list, but we only
want to report the error once and once we have an error we can return
early.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 560b3284 ("drm: kselftest for drm_mm and eviction")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110144031.7609-1-chris@chris-wilson.co.uk

drivers/gpu/drm/selftests/test-drm_mm.c

@@ -1274,13 +1274,19 @@ static bool evict_everything(struct drm_mm *mm,
 		if (drm_mm_scan_add_block(&scan, &e->node))
 			break;
 	}
+
+	err = 0;
 	list_for_each_entry(e, &evict_list, link) {
 		if (!drm_mm_scan_remove_block(&scan, &e->node)) {
+			if (!err) {
 				pr_err("Node %lld not marked for eviction!\n",
 				       e->node.start);
-			list_del(&e->link);
+				err = -EINVAL;
 			}
 		}
+	}
+	if (err)
+		return false;
 
 	list_for_each_entry(e, &evict_list, link)
 		drm_mm_remove_node(&e->node);