xfree: move xfree() function to xmalloc.c

Signed-off-by: whzhe <wanghongzhe@huawei.com>

libmisc/xmalloc.c

@@ -66,3 +66,10 @@
 {
 	return strcpy (xmalloc (strlen (str) + 1), str);
 }
+
+void xfree(void *ap)
+{
+	if (ap) {
+		free(ap);
+	}
+}