pwm: Fix setting period with #pwm-cells = <1> and of_pwm_single_xlate()

For drivers making use of of_pwm_single_xlate() (i.e. those that don't
pass a hwpwm index) and also don't pass flags, setting period was
wrongly skipped. This affects the pwm-pxa and ti-sn65dsi86 drivers.

Reported-by: Karel Balej <balejk@matfyz.cz>
Link: https://lore.kernel.org/r/D05IVTPYH35N.2CLDG6LSILRSN@matfyz.cz
Fixes: 40ade0c ("pwm: Let the of_xlate callbacks accept references without period")
Tested-by: Karel Balej <balejk@matfyz.cz>
Link: https://lore.kernel.org/r/20240329103544.545290-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Author: Uwe Kleine-König

drivers/pwm/core.c

@@ -443,7 +443,7 @@ of_pwm_single_xlate(struct pwm_chip *chip, const struct of_phandle_args *args)
 	if (IS_ERR(pwm))
 		return pwm;
 
-	if (args->args_count > 1)
+	if (args->args_count > 0)
 		pwm->args.period = args->args[0];
 
 	pwm->args.polarity = PWM_POLARITY_NORMAL;