iio: invensense: fix odr switching to same value

ODR switching happens in 2 steps, update to store the new value and then
apply when the ODR change flag is received in the data. When switching to
the same ODR value, the ODR change flag is never happening, and frequency
switching is blocked waiting for the never coming apply.

Fix the issue by preventing update to happen when switching to same ODR
value.

Fixes: 0ecc363 ("iio: make invensense timestamp module generic")
Cc: stable@vger.kernel.org
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://lore.kernel.org/r/20240524124851.567485-1-inv.git-commit@tdk.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: jmaneyrol-invn

drivers/iio/common/inv_sensors/inv_sensors_timestamp.c

@@ -60,11 +60,15 @@ EXPORT_SYMBOL_NS_GPL(inv_sensors_timestamp_init, IIO_INV_SENSORS_TIMESTAMP);
 int inv_sensors_timestamp_update_odr(struct inv_sensors_timestamp *ts,
 				     uint32_t period, bool fifo)
 {
+	uint32_t mult;
+
 	/* when FIFO is on, prevent odr change if one is already pending */
 	if (fifo && ts->new_mult != 0)
 		return -EAGAIN;
 
-	ts->new_mult = period / ts->chip.clock_period;
+	mult = period / ts->chip.clock_period;
+	if (mult != ts->mult)
+		ts->new_mult = mult;
 
 	return 0;
 }