iio: accel: add support for LIS302DL variant

Add support for STMicroelectronics LIS302DL accelerometer to the st_accel
framework.

Datasheet: https://www.st.com/resource/en/datasheet/lis302dl.pdf

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sicelo A. Mhlongo <absicsz@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220307132502.73854-4-absicsz@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>