page-types.c: fix name of unpoison interface

The page-types utility still uses an out of date name for the
unpoison interface: debugfs:hwpoison/renew-pfn
This patch renames and fixes it.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

Documentation/vm/page-types.c

@@ -478,7 +478,7 @@ static void prepare_hwpoison_fd(void)
 	}
 
 	if (opt_unpoison && !hwpoison_forget_fd) {
-		sprintf(buf, "%s/renew-pfn", hwpoison_debug_fs);
+		sprintf(buf, "%s/unpoison-pfn", hwpoison_debug_fs);
 		hwpoison_forget_fd = checked_open(buf, O_WRONLY);
 	}
 }