f2fs: initialize newly allocated dnode structure

This patch resolves Coverity #753112.

In practical, the existing code flow does not fall into the reported errorneous
path. But, anyway, let's avoid this for future.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/f2fs.h

@@ -211,11 +211,11 @@ struct dnode_of_data {
 static inline void set_new_dnode(struct dnode_of_data *dn, struct inode *inode,
 		struct page *ipage, struct page *npage, nid_t nid)
 {
+	memset(dn, 0, sizeof(*dn));
 	dn->inode = inode;
 	dn->inode_page = ipage;
 	dn->node_page = npage;
 	dn->nid = nid;
-	dn->inode_page_locked = 0;
 }
 
 /*