pwm: Make use of pwm_get_xxx() helpers where appropriate

Use the pwm_get_xxx() helpers instead of directly accessing the fields
in struct pwm_device. This will allow us to smoothly move to the atomic
update approach.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index b3b294d..0e4bd4e 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -114,7 +114,7 @@
 	u32 val;
 	int ret;
 
-	if (pwm_is_enabled(pwm) && (period_ns != pwm->period)) {
+	if (pwm_is_enabled(pwm) && (period_ns != pwm_get_period(pwm))) {
 		dev_err(chip->dev, "cannot change PWM period while enabled\n");
 		return -EBUSY;
 	}