dm: provide timer callback handlers the number of expirations

It is possible for multiple timeouts to occur in one mevent epoll
iteration. Providing the number of timer expirations to the timer
callback handlers can be useful. E.g., this could improve emulation of
timing-sensitive hardware components.

Tracked-On: #2319
Signed-off-by: Peter Fang <peter.fang@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>

devicemodel/hw/pci/wdt_i6300esb.c

@@ -110,7 +110,7 @@ static void start_wdt_timer(void);
  * action to guest OS
  */
 static void
-wdt_expired_handler(void *arg)
+wdt_expired_handler(void *arg, uint64_t nexp)
 {
 	struct pci_vdev *dev = (struct pci_vdev *)arg;