slub statistics: Fix check for DEACTIVATE_REMOTE_FREES

The remote frees are in the freelist of the page and not in the
percpu freelist.

Reviewed-by: Pekka Enberg <[e-mail]>
Signed-off-by: Christoph Lameter <[e-mail]>

mm/slub.c

···
 	struct page *page = c->page;
 	int tail = 1;
 
-	if (c->freelist)
+	if (page->freelist)
 		stat(c, DEACTIVATE_REMOTE_FREES);
 	/*
 	 * Merge cpu freelist into slab freelist. Typically we get here