drivers: pwm: pwm_nrf_sw: use shutdown task if available

Add a workaround for NRF52 anomaly 78: "High current consumption when
using timer STOP task only. Use the SHUTDOWN task instead."

Signed-off-by: Sven Depoorter <svndepoorter@gmail.com>

Author: Snevzor

drivers/pwm/pwm_nrf_sw.c

@@ -206,6 +206,9 @@ static int pwm_nrf_sw_set_cycles(const struct device *dev, uint32_t channel,
 			nrf_rtc_task_trigger(rtc, NRF_RTC_TASK_STOP);
 		} else {
 			nrf_timer_task_trigger(timer, NRF_TIMER_TASK_STOP);
+#if NRF_TIMER_HAS_SHUTDOWN
+			nrf_timer_task_trigger(timer, NRF_TIMER_TASK_SHUTDOWN);
+#endif
 		}
 
 		return 0;