Drivers: hv: vmbus: Teardown clockevent devices on module unload

Newly introduced clockevent devices made it impossible to unload hv_vmbus
module as clockevents_config_and_register() takes additional reverence to
the module. To make it possible again we do the following:
- avoid setting dev->owner for clockevent devices;
- implement hv_synic_clockevents_cleanup() doing clockevents_unbind_device();
- call it from vmbus_exit().

In theory hv_synic_clockevents_cleanup() can be merged with hv_synic_cleanup(),
however, we call hv_synic_cleanup() from smp_call_function_single() and this
doesn't work for clockevents_unbind_device() as it does such call on its own. I
opted for a separate function.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/vmbus_drv.c

@@ -1032,6 +1032,7 @@ static void __exit vmbus_exit(void)
 	int cpu;
 
 	vmbus_connection.conn_state = DISCONNECTED;
+	hv_synic_clockevents_cleanup();
 	hv_remove_vmbus_irq();
 	vmbus_free_channels();
 	bus_unregister(&hv_bus);