Revert "commander/navigator: remove param NAV_RCL_ACT"

This reverts commit 77ea4cebf41cd106fe771b9eb469aa2326339467.

src/modules/navigator/navigator_params.c

@@ -86,6 +86,24 @@ PARAM_DEFINE_FLOAT(NAV_ACC_RAD, 10.0f);
  */
 PARAM_DEFINE_INT32(NAV_DLL_ACT, 0);
 
+/**
+ * Set RC loss failsafe mode
+ *
+ * The RC loss failsafe will only be entered after a timeout,
+ * set by COM_RC_LOSS_T in seconds. If RC input checks have been disabled
+ * by setting the COM_RC_IN_MODE param it will not be triggered.
+ * Setting this parameter to 4 will enable CASA Outback Challenge rules,
+ * which are only recommended to participants of that competition.
+ *
+ * @value 0 Disabled
+ * @value 1 Loiter
+ * @value 2 Return to Land
+ * @value 3 Land at current position
+ *
+ * @group Mission
+ */
+PARAM_DEFINE_INT32(NAV_RCL_ACT, 0);
+
 /**
  * Airfield home Lat
  *