iio: imu: inv_mpu6050: fix FIFO parsing when empty

Now that we are reading the full FIFO in the interrupt handler,
it is possible to have an emply FIFO since we are still receiving
1 interrupt per data. Handle correctly this case instead of having
an error causing a reset of the FIFO.

Fixes: 0829edc ("iio: imu: inv_mpu6050: read the full fifo when processing data")
Cc: stable@vger.kernel.org
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://lore.kernel.org/r/20240219154825.90656-1-inv.git-commit@tdk.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: jmaneyrol-invn

drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c

@@ -109,6 +109,8 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p)
 	/* compute and process only all complete datum */
 	nb = fifo_count / bytes_per_datum;
 	fifo_count = nb * bytes_per_datum;
+	if (nb == 0)
+		goto end_session;
 	/* Each FIFO data contains all sensors, so same number for FIFO and sensor data */
 	fifo_period = NSEC_PER_SEC / INV_MPU6050_DIVIDER_TO_FIFO_RATE(st->chip_config.divider);
 	inv_sensors_timestamp_interrupt(&st->timestamp, fifo_period, nb, nb, pf->timestamp);