alinux: mm: remove unused variable

To fix the following build warning:
mm/memcontrol.c: In function ‘mem_cgroup_move_account’:
mm/memcontrol.c:5604:6: warning: unused variable ‘nid’ [-Wunused-variable]
  int nid = page_to_nid(page);
      ^

Fixes: 96298509 ("mm: thp: don't need care deferred split queue in memcg charge move path")
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NYang Shi <yang.shi@linux.alibaba.com>

mm/memcontrol.c

@@ -5601,7 +5601,6 @@ static int mem_cgroup_move_account(struct page *page,
 	unsigned int nr_pages = compound ? hpage_nr_pages(page) : 1;
 	int ret;
 	bool anon;
-	int nid = page_to_nid(page);
 
 	VM_BUG_ON(from == to);
 	VM_BUG_ON_PAGE(PageLRU(page), page);