pwm: sprd: Refuse requests with unsupported polarity

The driver only supports normal polarity and so should refuse requests
for inversed polarity.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-sprd.c

@@ -164,6 +164,9 @@ static int sprd_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	struct pwm_state *cstate = &pwm->state;
 	int ret;
 
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
 	if (state->enabled) {
 		if (!cstate->enabled) {
 			/*