gpio: mvebu/pwm: Refuse requests with inverted polarity

The driver doesn't take struct pwm_state::polarity into account when
configuring the hardware, so refuse requests for inverted polarity.

Fixes: 757642f9 ("gpio: mvebu: Add limited PWM support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

drivers/gpio/gpio-mvebu.c

@@ -707,6 +707,9 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	unsigned long flags;
 	unsigned int on, off;
 
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
 	val = (unsigned long long) mvpwm->clk_rate * state->duty_cycle;
 	do_div(val, NSEC_PER_SEC);
 	if (val > UINT_MAX + 1ULL)