freebsd_network(): call uninit_hard_clock() on uninit

Not uninstalling the timer hook could lead to a crash after unloading/
reloading the driver.

src/libs/compat/freebsd_network/driver.c

@@ -266,6 +266,7 @@ _fbsd_uninit_drivers(driver_t *drivers[])
 		uninit_taskqueues();
 	uninit_callout();
 	uninit_mutexes();
+	uninit_hard_clock();
 
 	put_module(B_PCI_MODULE_NAME);
 	if (gPCIx86 != NULL)