WorkQueue: Fix up arch-specific work items where possible

Fix up arch-specific work items where possible to use the new work_struct and
delayed_work structs.

Three places that enqueue bits of their stack and then return have been marked
with #error as this is not permitted.

Signed-Off-By: David Howells <dhowells@redhat.com>

arch/um/drivers/net_kern.c

@@ -99,6 +99,7 @@ irqreturn_t uml_net_interrupt(int irq, void *dev_id)
 		 * same device, since it tests for (dev->flags & IFF_UP). So
 		 * there's no harm in delaying the device shutdown. */
 		schedule_work(&close_work);
+#error this is not permitted - close_work will go out of scope
 		goto out;
 	}
 	reactivate_fd(lp->fd, UM_ETH_IRQ);