f2fs: check return value during recovery

This patch resolves Coverity #753102:

>>> No check of the return value of "f2fs_add_link(&dent, inode)".
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/recovery.c

@@ -67,7 +67,7 @@ static int recover_dentry(struct page *ipage, struct inode *inode)
 		kunmap(page);
 		f2fs_put_page(page, 0);
 	} else {
-		f2fs_add_link(&dent, inode);
+		err = f2fs_add_link(&dent, inode);
 	}
 	iput(dir);
 out: