DataFlash: move _initialised into DataFlash_Backend

libraries/DataFlash/DataFlash_Backend.cpp

@@ -268,6 +268,9 @@ bool DataFlash_Backend::WritesOK() const
     if (!_front.vehicle_is_armed() && !_front.log_while_disarmed()) {
         return false;
     }
+    if (!_initialised) {
+        return false;
+    }
 
     return true;
 }

libraries/DataFlash/DataFlash_Backend.h

@@ -157,6 +157,8 @@ protected:
     // must be called when a new log is being started:
     virtual void start_new_log_reset_variables();
 
+    bool _initialised;
+
 private:
 
     uint32_t _last_periodic_1Hz;

libraries/DataFlash/DataFlash_File.cpp

@@ -53,7 +53,6 @@ DataFlash_File::DataFlash_File(DataFlash_Class &front,
     _read_fd_log_num(0),
     _read_offset(0),
     _write_offset(0),
-    _initialised(false),
     _open_error(false),
     _log_directory(log_directory),
     _cached_oldest_log(0),
@@ -520,9 +519,6 @@ bool DataFlash_File::WritesOK() const
     if (_write_fd == -1) {
         return false;
     }
-    if (!_initialised) {
-        return false;
-    }
     if (_open_error) {
         return false;
     }

libraries/DataFlash/DataFlash_File.h

@@ -83,7 +83,6 @@ private:
     uint16_t _read_fd_log_num;
     uint32_t _read_offset;
     uint32_t _write_offset;
-    volatile bool _initialised;
     volatile bool _open_error;
     const char *_log_directory;
 

libraries/DataFlash/DataFlash_MAVLink.cpp

@@ -124,9 +124,6 @@ bool DataFlash_MAVLink::WritesOK() const
     if (!DataFlash_Backend::WritesOK()) {
         return false;
     }
-    if (!_initialised) {
-        return false;
-    }
     if (!_sending_to_client) {
         return false;
     }

libraries/DataFlash/DataFlash_MAVLink.h

@@ -131,8 +131,6 @@ private:
     uint8_t _target_system_id;
     uint8_t _target_component_id;
 
-    bool _initialised;
-
     // this controls the maximum number of blocks we will push from
     // the pending and send queues in any call to push_log_blocks.
     // push_log_blocks is called by periodic_tasks.  Each block is 200