AC_InputManager: removed create() method for objects

See discussion here:

  https://github.com/ArduPilot/ardupilot/issues/7331

we were getting some uninitialised variables. While it only showed up in
AP_SbusOut, it means we can't be sure it won't happen on other objects,
so safest to remove the approach

Thanks to assistance from Lucas, Peter and Francisco

libraries/AC_InputManager/AC_InputManager.h

@@ -11,9 +11,10 @@
 /// @brief  Class managing the pilot's control inputs
 class AC_InputManager{
 public:
-    static AC_InputManager create() { return AC_InputManager{}; }
-
-    constexpr AC_InputManager(AC_InputManager &&other) = default;
+    AC_InputManager() {
+        // setup parameter defaults
+        AP_Param::setup_object_defaults(this, var_info);
+    }
 
     /* Do not allow copies */
     AC_InputManager(const AC_InputManager &other) = delete;
@@ -23,11 +24,6 @@ public:
     void set_loop_rate(uint16_t loop_rate) { _loop_rate = loop_rate; }
 
 protected:
-    AC_InputManager() {
-        // setup parameter defaults
-        AP_Param::setup_object_defaults(this, var_info);
-    }
-
     // internal variables
     uint16_t            _loop_rate;             // rate at which output() function is called (normally 400hz)
 

libraries/AC_InputManager/AC_InputManager_Heli.h

@@ -16,9 +16,13 @@
 /// @brief  Class managing the pilot's control inputs   for Conventional Helicopter
 class AC_InputManager_Heli : public AC_InputManager {
 public:
-    static AC_InputManager_Heli create() { return AC_InputManager_Heli{}; }
-
-    constexpr AC_InputManager_Heli(AC_InputManager_Heli &&other) = default;
+    // Constructor
+    AC_InputManager_Heli()
+        : AC_InputManager()
+    {
+        // setup parameter defaults
+        AP_Param::setup_object_defaults(this, var_info);
+    }
 
     /* Do not allow copies */
     AC_InputManager_Heli(const AC_InputManager_Heli &other) = delete;
@@ -35,15 +39,6 @@ public:
 
     static const struct AP_Param::GroupInfo        var_info[];
 
-protected:
-    // Constructor
-    AC_InputManager_Heli()
-        : AC_InputManager()
-    {
-        // setup parameter defaults
-        AP_Param::setup_object_defaults(this, var_info);
-    }
-
 private:
     struct InputManagerHeliFlags {
         uint8_t use_stab_col        :   1;  // 1 if we should use Stabilise mode collective range, 0 for Acro range