Export this function in preparation for the fix in veml6030.c, where the
total gain can be used to ease the calculation of the processed value of
the IIO_LIGHT channel compared to acquiring the scale in NANO.
Suggested-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx>