um: Remove obsolete reenable_XX calls

reenable_fd has been a NOP since the introduction of the EPOLL
based interrupt controller.
reenable_channel() is no longer needed as the flow control is
now handled via the write IRQs on the channel.

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/net_kern.c

@@ -137,8 +137,6 @@ static irqreturn_t uml_net_interrupt(int irq, void *dev_id)
 		schedule_work(&lp->work);
 		goto out;
 	}
-	reactivate_fd(lp->fd, UM_ETH_IRQ);
-
 out:
 	spin_unlock(&lp->lock);
 	return IRQ_HANDLED;