Drivers: hv: balloon: Make the balloon driver not unloadable

The balloon driver is stateful. For instance, it needs to keep track of pages
that have been ballooned out to properly post pressure reports. This state cannot
be re-constructed if the driver were to be unloaded and subsequently loaded.
Furthermore, as we support memory hot-add as part of this driver, this driver becomes
even more stateful and this state cannot be re-created. Make the balloon driver
unloadable to deal with this issue.
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: NHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/hv_balloon.c

@@ -1096,14 +1096,7 @@ static int __init init_balloon_drv(void)
 	return vmbus_driver_register(&balloon_drv);
 }
 
-static void exit_balloon_drv(void)
-{
-
-	vmbus_driver_unregister(&balloon_drv);
-}
-
 module_init(init_balloon_drv);
-module_exit(exit_balloon_drv);
 
 MODULE_DESCRIPTION("Hyper-V Balloon");
 MODULE_VERSION(HV_DRV_VERSION);