iio: imu: st_lsm6dsx: fix possible lockup in st_lsm6dsx_read_tagged_fifo

Prevent st_lsm6dsx_read_tagged_fifo from falling in an infinite loop in
case pattern_len is equal to zero and the device FIFO is not empty.

Fixes: 801a6e0 ("iio: imu: st_lsm6dsx: add support to LSM6DSO")
Signed-off-by: Silvano Seva <s.seva@4sigma.it>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250311085030.3593-4-s.seva@4sigma.it
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: Silvano Seva

drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c

@@ -626,6 +626,9 @@ int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
 	if (!fifo_len)
 		return 0;
 
+	if (!pattern_len)
+		pattern_len = ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
+
 	for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
 		err = st_lsm6dsx_read_block(hw,
 					    ST_LSM6DSX_REG_FIFO_OUT_TAG_ADDR,