Do not attach children of owc_gpiobus until interrupts are working.

The children of the bus need to do IO on the bus to probe for hardware
presence.  Doing IO means timing the bus states using sbinuptime(), and
that requires working timecounters, which are not initialized until after
device attachment has completed.

PR:		242526

sys/dev/ow/owc_gpiobus.c

@@ -131,7 +131,7 @@ owc_gpiobus_attach(device_t dev)
 		free(kids, M_TEMP);
 	if (nkid == 0)
 		device_add_child(dev, "ow", -1);
-	bus_generic_attach(dev);
+	config_intrhook_oneshot((ich_func_t)bus_generic_attach, dev);
 
 	return (0);
 }