pwm: atmel-tcb: Simplify checking the companion output

The two outputs provided by the supported hardware share some settings,
so access to the other PWM is required when one of them is configured.

Instead of an explicit if to deterimine the other PWM just use
hwpwm ^ 1. Further atcbpwm is never NULL, so drop the corresponding
check.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20240709101806.52394-4-u.kleine-koenig@baylibre.comSigned-off-by: Uwe Kleine-König <ukleinek@kernel.org>

drivers/pwm/pwm-atmel-tcb.c

@@ -260,7 +260,8 @@ static int atmel_tcb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 {
 	struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
 	struct atmel_tcb_pwm_device *tcbpwm = &tcbpwmc->pwms[pwm->hwpwm];
-	struct atmel_tcb_pwm_device *atcbpwm = NULL;
+	/* companion PWM sharing register values period and div */
+	struct atmel_tcb_pwm_device *atcbpwm = &tcbpwmc->pwms[pwm->hwpwm ^ 1];
 	int i = 0;
 	int slowclk = 0;
 	unsigned period;
@@ -305,11 +306,6 @@ static int atmel_tcb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	duty = div_u64(duty_ns, min);
 	period = div_u64(period_ns, min);
 
-	if (pwm->hwpwm == 0)
-		atcbpwm = &tcbpwmc->pwms[1];
-	else
-		atcbpwm = &tcbpwmc->pwms[0];
-
 	/*
 	 * PWM devices provided by the TCB driver are grouped by 2.
 	 * PWM devices in a given group must be configured with the
@@ -318,8 +314,7 @@ static int atmel_tcb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	 * We're checking the period value of the second PWM device
 	 * in this group before applying the new config.
 	 */
-	if ((atcbpwm && atcbpwm->duty > 0 &&
-			atcbpwm->duty != atcbpwm->period) &&
+	if ((atcbpwm->duty > 0 && atcbpwm->duty != atcbpwm->period) &&
 		(atcbpwm->div != i || atcbpwm->period != period)) {
 		dev_err(pwmchip_parent(chip),
 			"failed to configure period_ns: PWM group already configured with a different value\n");