f2fs: use inner macro GFP_F2FS_ZERO for simplification

Use inner macro GFP_F2FS_ZERO to instead of GFP_NOFS | __GFP_ZERO for
simplification of code.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 0855168..099f06f 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1577,7 +1577,7 @@
 
 	for (; page_idx < start + nrpages; page_idx++) {
 		/* alloc temporal page for read node summary info*/
-		page = alloc_page(GFP_NOFS | __GFP_ZERO);
+		page = alloc_page(GFP_F2FS_ZERO);
 		if (!page) {
 			struct page *tmp;
 			list_for_each_entry_safe(page, tmp, pages, lru) {