AP_Mount: remove redundant constructors

just copy in the one from the parent class

libraries/AP_Mount/AP_Mount_Alexmos.h

@@ -64,9 +64,7 @@ class AP_Mount_Alexmos : public AP_Mount_Backend
 {
 public:
     //constructor
-    AP_Mount_Alexmos(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance):
-        AP_Mount_Backend(frontend, params, instance)
-    {}
+    using AP_Mount_Backend::AP_Mount_Backend;
 
     // init - performs any required initialisation for this instance
     void init() override;

libraries/AP_Mount/AP_Mount_Gremsy.cpp

@@ -11,10 +11,6 @@ extern const AP_HAL::HAL& hal;
 #define AP_MOUNT_GREMSY_SEARCH_MS  60000    // search for gimbal for 1 minute after startup
 #define AP_MOUNT_GREMSY_ATTITUDE_INTERVAL_US    20000  // send ATTITUDE and AUTOPILOT_STATE_FOR_GIMBAL_DEVICE at 50hz
 
-AP_Mount_Gremsy::AP_Mount_Gremsy(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance) :
-    AP_Mount_Backend(frontend, params, instance)
-{}
-
 // update mount position
 void AP_Mount_Gremsy::update()
 {

libraries/AP_Mount/AP_Mount_Gremsy.h

@@ -16,7 +16,7 @@ class AP_Mount_Gremsy : public AP_Mount_Backend
 
 public:
     // Constructor
-    AP_Mount_Gremsy(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance);
+    using AP_Mount_Backend::AP_Mount_Backend;
 
     // init
     void init() override {}

libraries/AP_Mount/AP_Mount_SToRM32.cpp

@@ -9,11 +9,6 @@ extern const AP_HAL::HAL& hal;
 #define AP_MOUNT_STORM32_RESEND_MS  1000    // resend angle targets to gimbal once per second
 #define AP_MOUNT_STORM32_SEARCH_MS  60000   // search for gimbal for 1 minute after startup
 
-AP_Mount_SToRM32::AP_Mount_SToRM32(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance) :
-    AP_Mount_Backend(frontend, params, instance),
-    _chan(MAVLINK_COMM_0)
-{}
-
 // update mount position - should be called periodically
 void AP_Mount_SToRM32::update()
 {

libraries/AP_Mount/AP_Mount_SToRM32.h

@@ -15,7 +15,7 @@ class AP_Mount_SToRM32 : public AP_Mount_Backend
 
 public:
     // Constructor
-    AP_Mount_SToRM32(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance);
+    using AP_Mount_Backend::AP_Mount_Backend;
 
     // init - performs any required initialisation for this instance
     void init() override {}
@@ -43,7 +43,7 @@ private:
     bool _initialised;              // true once the driver has been initialised
     uint8_t _sysid;                 // sysid of gimbal
     uint8_t _compid;                // component id of gimbal
-    mavlink_channel_t _chan;        // mavlink channel used to communicate with gimbal
+    mavlink_channel_t _chan = MAVLINK_COMM_0;        // mavlink channel used to communicate with gimbal
     uint32_t _last_send;            // system time of last do_mount_control sent to gimbal
     MountTarget _angle_rad;         // latest angle target
 };

libraries/AP_Mount/AP_Mount_SToRM32_serial.cpp

@@ -6,11 +6,6 @@
 #include <GCS_MAVLink/include/mavlink/v2.0/checksum.h>
 #include <AP_SerialManager/AP_SerialManager.h>
 
-AP_Mount_SToRM32_serial::AP_Mount_SToRM32_serial(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance) :
-    AP_Mount_Backend(frontend, params, instance),
-    _reply_type(ReplyType_UNKNOWN)
-{}
-
 // init - performs any required initialisation for this instance
 void AP_Mount_SToRM32_serial::init()
 {

libraries/AP_Mount/AP_Mount_SToRM32_serial.h

@@ -18,7 +18,7 @@ class AP_Mount_SToRM32_serial : public AP_Mount_Backend
 
 public:
     // Constructor
-    AP_Mount_SToRM32_serial(AP_Mount &frontend, AP_Mount_Params &params, uint8_t instance);
+    using AP_Mount_Backend::AP_Mount_Backend;
 
     // init - performs any required initialisation for this instance
     void init() override;
@@ -135,7 +135,7 @@ private:
 
     uint8_t _reply_length;
     uint8_t _reply_counter;
-    ReplyType _reply_type;
+    ReplyType _reply_type = ReplyType_UNKNOWN;
 
 
     union PACKED SToRM32_reply {