task_wdt: start feeding hardware watchdog immediately after init

Without this, the hardware watchdog would expire if no task watchdogs were
registered within one hardware watchdog period after init. Start the
background channel immediately after init to avoid this.

Signed-off-by: Armin Brauns <armin.brauns@embedded-solutions.at>

subsys/task_wdt/task_wdt.c

@@ -147,6 +147,7 @@ int task_wdt_init(const struct device *hw_wdt)
 	}
 
 	k_timer_init(&timer, task_wdt_trigger, NULL);
+	schedule_next_timeout(sys_clock_tick_get());
 
 	return 0;
 }