alinux: mm/thp: remove unused variable 'pgdata' in split_huge_page_to_list()

This fixes the following build warning:
mm/huge_memory.c: In function ‘split_huge_page_to_list’:
mm/huge_memory.c:2656:22: warning: unused variable ‘pgdata’ [-Wunused-variable]
  struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
                      ^

Fixes: 6c52af5ee5c5 ("mm: thp: extract split_queue_* into a struct")
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NXunlei Pang <xlpang@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>

mm/huge_memory.c

@@ -2659,7 +2659,6 @@ bool can_split_huge_page(struct page *page, int *pextra_pins)
 int split_huge_page_to_list(struct page *page, struct list_head *list)
 {
 	struct page *head = compound_head(page);
-	struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
 	struct deferred_split *ds_queue = get_deferred_split_queue(page);
 	struct anon_vma *anon_vma = NULL;
 	struct address_space *mapping = NULL;