Drivers: hv: balloon: add a fall through comment to hv_memory_notifier()

Coverity scan gives a warning when there is fall through in a switch
without a comment. This fall through is intentional as ol_waitevent needs
to be completed to unblock hv_mem_hot_add() allowing it to process next
requests regardless of the result of if we were able to online this block.

Reported-by: Stephen Hemminger <sthemmin@microsoft.com>
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/hv_balloon.c

@@ -587,6 +587,7 @@ static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
 		spin_lock_irqsave(&dm_device.ha_lock, flags);
 		dm_device.num_pages_onlined += mem->nr_pages;
 		spin_unlock_irqrestore(&dm_device.ha_lock, flags);
+		/* Fall through */
 	case MEM_CANCEL_ONLINE:
 		if (dm_device.ha_waiting) {
 			dm_device.ha_waiting = false;