trace: top tracer in oops_enter()

If trace_printk_on_oops is set we lose interesting trace information
when the tracer is enabled across oops handling and printing. We want
the trace which might give us information _WHY_ we oopsed.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/panic.c

@@ -301,6 +301,7 @@ int oops_may_print(void)
  */
 void oops_enter(void)
 {
+	tracing_off();
 	/* can't trust the integrity of the kernel anymore: */
 	debug_locks_off();
 	do_oops_enter_exit();