trace_irq_handler_exit — called immediately after the irq action handler returns
|struct irqaction * action,|
ret value is set to IRQ_HANDLED, then we know that the corresponding
action->handler scuccessully handled this irq. Otherwise, the irq might be
a shared irq line, or the irq was not handled successfully. Can be used in
conjunction with the irq_handler_entry to understand irq handler latencies.