Update the IRQ stats.

def update(self):
        """Update the IRQ stats."""
        # Init new stats
        stats = self.get_init_value()

        # IRQ plugin only available on GNU/Linux
        if not LINUX:
            return self.stats

        if self.input_method == 'local':
            # Grab the stats
            stats = self.irq.get()

        elif self.input_method == 'snmp':
            # not available
            pass

        # Get the TOP 5 (by rate/s)
        stats = sorted(stats,
                       key=operator.itemgetter('irq_rate'),
                       reverse=True)[:5]

        # Update the stats
        self.stats = stats

        return self.stats