AP_Camera: 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/AP_Camera/AP_Camera.h

@@ -31,15 +31,17 @@
 class AP_Camera {
 
 public:
-    static AP_Camera create(AP_Relay *obj_relay,
+    AP_Camera(AP_Relay *obj_relay, uint32_t _log_camera_bit, const struct Location &_loc, const AP_AHRS &_ahrs)
-                            uint32_t _log_camera_bit,
+        : _trigger_counter(0) // count of number of cycles shutter has been held open
-                            const struct Location &_loc,
+        , _image_index(0)
-                            const AP_AHRS &_ahrs) {
+        , log_camera_bit(_log_camera_bit)
-        return AP_Camera{obj_relay, _log_camera_bit, _loc, _ahrs};
+        , current_loc(_loc)
+        , ahrs(_ahrs)
+    {
+        AP_Param::setup_object_defaults(this, var_info);
+        _apm_relay = obj_relay;
     }
 
-    constexpr AP_Camera(AP_Camera &&other) = default;
-
     /* Do not allow copies */
     AP_Camera(const AP_Camera &other) = delete;
     AP_Camera &operator=(const AP_Camera&) = delete;
@@ -71,17 +73,6 @@ public:
     void set_is_auto_mode(bool enable) { _is_in_auto_mode = enable; }
 
 private:
-    AP_Camera(AP_Relay *obj_relay, uint32_t _log_camera_bit, const struct Location &_loc, const AP_AHRS &_ahrs)
-        : _trigger_counter(0) // count of number of cycles shutter has been held open
-        , _image_index(0)
-        , log_camera_bit(_log_camera_bit)
-        , current_loc(_loc)
-        , ahrs(_ahrs)
-    {
-        AP_Param::setup_object_defaults(this, var_info);
-        _apm_relay = obj_relay;
-    }
-
     AP_Int8         _trigger_type;      // 0:Servo,1:Relay
     AP_Int8         _trigger_duration;  // duration in 10ths of a second that the camera shutter is held open
     AP_Int8         _relay_on;          // relay value to trigger camera