Rover: add comment to unused param enum entries

APMrover2/Parameters.h

@@ -34,8 +34,8 @@ public:
         k_param_relay,
         k_param_BoardConfig,
         k_param_pivot_turn_angle,
-        k_param_rc_13_old,
-        k_param_rc_14_old,
+        k_param_rc_13_old,  // unused
+        k_param_rc_14_old,  // unused
 
         // IO pins
         k_param_rssi_pin = 20,  // unused, replaced by rssi_ library parameters
@@ -65,15 +65,15 @@ public:
         k_param_gcs1,               // stream rates for uartC
         k_param_sysid_this_mav,
         k_param_sysid_my_gcs,
-        k_param_serial0_baud_old,
-        k_param_serial1_baud_old,
+        k_param_serial0_baud_old,   // unused
+        k_param_serial1_baud_old,   // unused
         k_param_telem_delay,
         k_param_skip_gyro_cal,      // unused
         k_param_gcs2,               // stream rates for uartD
-        k_param_serial2_baud_old,
+        k_param_serial2_baud_old,   // unused
         k_param_serial2_protocol,   // deprecated, can be deleted
         k_param_serial_manager,     // serial manager library
-        k_param_cli_enabled_old,
+        k_param_cli_enabled_old,    // unused
         k_param_gcs3,
         k_param_gcs_pid_mask,
 
@@ -100,8 +100,8 @@ public:
         //
         // 150: Navigation parameters
         //
-        k_param_crosstrack_gain = 150,
-        k_param_crosstrack_entry_angle,
+        k_param_crosstrack_gain = 150,  // unused
+        k_param_crosstrack_entry_angle, // unused
         k_param_speed_cruise,
         k_param_speed_turn_gain,
         k_param_speed_turn_dist,    // unused
@@ -114,14 +114,14 @@ public:
         //
         // 160: Radio settings
         //
-        k_param_rc_1_old = 160,
-        k_param_rc_2_old,
-        k_param_rc_3_old,
-        k_param_rc_4_old,
-        k_param_rc_5_old,
-        k_param_rc_6_old,
-        k_param_rc_7_old,
-        k_param_rc_8_old,
+        k_param_rc_1_old = 160, // unused
+        k_param_rc_2_old,       // unused
+        k_param_rc_3_old,       // unused
+        k_param_rc_4_old,       // unused
+        k_param_rc_5_old,       // unused
+        k_param_rc_6_old,       // unused
+        k_param_rc_7_old,       // unused
+        k_param_rc_8_old,       // unused
 
         // throttle control
         k_param_throttle_min_old = 170, // unused
@@ -184,10 +184,10 @@ public:
         k_param_pidSpeedThrottle_old,   // unused
 
         // high RC channels
-        k_param_rc_9_old = 235,
-        k_param_rc_10_old,
-        k_param_rc_11_old,
-        k_param_rc_12_old,
+        k_param_rc_9_old = 235, // unused
+        k_param_rc_10_old,      // unused
+        k_param_rc_11_old,      // unused
+        k_param_rc_12_old,      // unusedS
 
         // other objects
         k_param_sitl = 240,