iio: imu: st_lsm6dsx: fix possible lockup in st_lsm6dsx_read_fifo

iio: imu: st_lsm6dsx: fix possible lockup in st_lsm6dsx_read_fifo

Prevent st_lsm6dsx_read_fifo from falling in an infinite loop in case
pattern_len is equal to zero and the device FIFO is not empty.

Fixes: 290a6ce11d93 ("iio: imu: add support to lsm6dsx driver")
Signed-off-by: Silvano Seva <s.seva@4sigma.it>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250311085030.3593-2-s.seva@4sigma.it
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>