iio: light: ltrf216a: Return floating point values

For better precision of input light intesity, return floating point
values through sysfs instead of an integer value

Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Link: https://lore.kernel.org/r/20231107192005.285534-1-shreeya.patel@collabora.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>