Remove a variable that caused a compiler warning

weather-sensor/firmware/bme280_interface.c

 /* Get one measurement in forced mode */
 void BME280_Get_Measurement(struct bme280_data * data)
 {
-	int8_t rslt = BME280_OK;
-
-	rslt = bme280_set_sensor_mode(BME280_FORCED_MODE, &deviceStructure);
+	bme280_set_sensor_mode(BME280_FORCED_MODE, &deviceStructure);
 	deviceStructure.delay_ms(req_delay);
-	rslt = bme280_get_sensor_data(BME280_ALL, data, &deviceStructure);
+	bme280_get_sensor_data(BME280_ALL, data, &deviceStructure);
 }
 
 /* Implementation of the interface function needed by the BME280 library */