Land detector: Turn throttle range parameter into proper user-configurable parameter

src/modules/land_detector/land_detector_params.c

@@ -88,6 +88,22 @@ PARAM_DEFINE_FLOAT(LNDMC_ROT_MAX, 20.0f);
  */
 PARAM_DEFINE_FLOAT(LNDMC_FFALL_THR, 2.0f);
 
+/**
+ * Multicopter sub-hover throttle scaling
+ *
+ * The range between throttle_min and throttle_hover is scaled
+ * by this parameter to define how close to minimum throttle
+ * the current throttle value needs to be in order to get
+ * accepted as landed.
+ *
+ * @min 0.05
+ * @max 0.5
+ * @decimal 2
+ *
+ * @group Land Detector
+ */
+PARAM_DEFINE_FLOAT(LNDMC_THR_RANGE, 0.1f);
+
 /**
  * Multicopter free-fall trigger time
  *