pwm: stm32: Fix complementary output in round_waveform_tohw()

When the timer supports complementary output, the CCxNE bit must be set
additionally to the CCxE bit. So to not overwrite the latter use |=
instead of = to set the former.

Fixes: deaba9c ("pwm: stm32: Implementation of the waveform callbacks")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20241217150021.2030213-1-fabrice.gasnier@foss.st.com
[ukleinek: Slightly improve commit log]
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

Author: Fabrice Gasnier

drivers/pwm/pwm-stm32.c

@@ -84,7 +84,7 @@ static int stm32_pwm_round_waveform_tohw(struct pwm_chip *chip,
 
 	wfhw->ccer = TIM_CCER_CCxE(ch + 1);
 	if (priv->have_complementary_output)
-		wfhw->ccer = TIM_CCER_CCxNE(ch + 1);
+		wfhw->ccer |= TIM_CCER_CCxNE(ch + 1);
 
 	rate = clk_get_rate(priv->clk);