iio: gts-helper: export iio_gts_get_total_gain()

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 <[e-mail]>
Signed-off-by: Javier Carrasco <[e-mail]>
Reviewed-by: Matti Vaittinen <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/industrialio-gts-helper.c

···
 }
 EXPORT_SYMBOL_NS_GPL(iio_gts_find_gain_time_sel_for_scale, "IIO_GTS_HELPER");
 
-static int iio_gts_get_total_gain(struct iio_gts *gts, int gain, int time)
+/**
+ * iio_gts_get_total_gain - Fetch total gain for given HW-gain and time
+ * @gts:	Gain time scale descriptor
+ * @gain:	HW-gain for which the total gain is searched for
+ * @time:	Integration time for which the total gain is searched for
+ *
+ * Return: total gain on success and -EINVAL on error.
+ */
+int iio_gts_get_total_gain(struct iio_gts *gts, int gain, int time)
 {
 	const struct iio_itime_sel_mul *itime;
 
···
 
 	return gain * itime->mul;
 }
+EXPORT_SYMBOL_NS_GPL(iio_gts_get_total_gain, "IIO_GTS_HELPER");
 
 static int iio_gts_get_scale_linear(struct iio_gts *gts, int gain, int time,
 				    u64 *scale)

include/linux/iio/iio-gts-helper.h

···
 			     int *length);
 int iio_gts_avail_scales_for_time(struct iio_gts *gts, int time,
 				  const int **vals, int *type, int *length);
+int iio_gts_get_total_gain(struct iio_gts *gts, int gain, int time);
 
 #endif