staging: iio: tsl2x7x: add range checking to three sysfs attributes

The sysfs attributes in_illuminance0_target_input,
in_illuminance0_calibrate, and in_proximity0_calibrate did not have
proper range checking in place so this patch adds the correct range
checks.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>