tracing: do not leak kernel addresses

CVE-2017-0630

This likely breaks tracing tools like trace-cmd.  It logs in the same
format but now addresses are all 0x0.

Change-Id: Ib8fa0f8d0a5c898be9bafae2e18b40dd373969c0

kernel/trace/trace_printk.c

@@ -272,7 +272,7 @@ static int t_show(struct seq_file *m, void *v)
 	const char *str = *fmt;
 	int i;
 
-	seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt);
+	seq_printf(m, "0x%lx : \"", 0L);
 
 	/*
 	 * Tabs and new lines need to be converted.