iio: trigger: stm32-timer: fix a corner case to write preset

Balance timer start routine that sets ARPE: clear it in stop routine.
This fixes a corner case, when timer is used successively as trigger
(with sampling_frequency start/stop routines), then as a counter
(with preset).

Fixes: 93fbe91 ("iio: Add STM32 timer trigger driver")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: Fabrice Gasnier

drivers/iio/trigger/stm32-timer-trigger.c

@@ -174,6 +174,7 @@ static void stm32_timer_stop(struct stm32_timer_trigger *priv)
 		clk_disable(priv->clk);
 
 	/* Stop timer */
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, 0);
 	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
 	regmap_write(priv->regmap, TIM_PSC, 0);
 	regmap_write(priv->regmap, TIM_ARR, 0);