genesys: Fix incorrect scan exposure setup on gl841

When sensor exposure values are significantly different from each other
the total scan exposure will be too low leading to the device becoming
confused and significantly

backend/genesys/gl841.cpp

@@ -956,9 +956,9 @@ static int gl841_exposure_time(Genesys_Device *dev, const Genesys_Sensor& sensor
     int led_exposure = 0;
     if (dev->model->is_cis) {
         unsigned dummy = dev->reg.find_reg(0x19).value;
-        unsigned min_sensor_exposure = std::min({sensor.exposure.red, sensor.exposure.green,
+        unsigned max_sensor_exposure = std::max({sensor.exposure.red, sensor.exposure.green,
                                                  sensor.exposure.blue});
-        led_exposure = dummy + min_sensor_exposure;
+        led_exposure = dummy + max_sensor_exposure;
     }
     return sanei_genesys_exposure_time2(dev, profile, slope_dpi,
                                         start + used_pixels,/*+tgtime? currently done in sanei_genesys_exposure_time2 with tgtime = 32 pixel*/