pwm: Don't use memcmp() to compare state variables

Given that struct pwm_state is sparse (at least on some platforms),
variables of this type might represent the same state because all fields
are pairwise identical but still memcmp() returns a difference because
some of the unused bits are different.

To prevent surprises compare member by member instead of the whole
occupied memory.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/core.c

@@ -472,7 +472,10 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
 	    state->duty_cycle > state->period)
 		return -EINVAL;
 
-	if (!memcmp(state, &pwm->state, sizeof(*state)))
+	if (state->period == pwm->state.period &&
+	    state->duty_cycle == pwm->state.duty_cycle &&
+	    state->polarity == pwm->state.polarity &&
+	    state->enabled == pwm->state.enabled)
 		return 0;
 
 	if (pwm->chip->ops->apply) {