pwm: stm32: Use 3 cells ->of_xlate()

STM32 Timers support generic 3 cells PWM to encode PWM number, period
and polarity.

Fixes: 7edf7369 ("pwm: Add driver for STM32 plaftorm")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-stm32.c

@@ -608,6 +608,8 @@ static int stm32_pwm_probe(struct platform_device *pdev)
 	priv->regmap = ddata->regmap;
 	priv->clk = ddata->clk;
 	priv->max_arr = ddata->max_arr;
+	priv->chip.of_xlate = of_pwm_xlate_with_flags;
+	priv->chip.of_pwm_n_cells = 3;
 
 	if (!priv->regmap || !priv->clk)
 		return -EINVAL;