DataFlash: replace unused AFF with actual in PID_Info

libraries/DataFlash/DataFlash.h

@@ -158,11 +158,11 @@ public:
     // This structure provides information on the internal member data of a PID for logging purposes
     struct PID_Info {
         float desired;
+        float actual;
         float P;
         float I;
         float D;
         float FF;
-        float AFF;
     };
 
     void Log_Write_PID(uint8_t msg_type, const PID_Info &info);

libraries/DataFlash/LogFile.cpp

@@ -1589,11 +1589,11 @@ void DataFlash_Class::Log_Write_PID(uint8_t msg_type, const PID_Info &info)
         LOG_PACKET_HEADER_INIT(msg_type),
         time_us         : AP_HAL::micros64(),
         desired         : info.desired,
+        actual          : info.actual,
         P               : info.P,
         I               : info.I,
         D               : info.D,
-        FF              : info.FF,
-        AFF             : info.AFF
+        FF              : info.FF
     };
     WriteBlock(&pkt, sizeof(pkt));
 }

libraries/DataFlash/LogStructure.h

@@ -665,11 +665,11 @@ struct PACKED log_PID {
     LOG_PACKET_HEADER;
     uint64_t time_us;
     float   desired;
+    float   actual;
     float   P;
     float   I;
     float   D;
     float   FF;
-    float   AFF;
 };
 
 struct PACKED log_Current {
@@ -1125,7 +1125,7 @@ struct PACKED log_DSTL {
 #define MAG_UNITS "sGGGGGGGGG-s"
 #define MAG_MULTS "FCCCCCCCCC-F"
 
-#define PID_LABELS "TimeUS,Des,P,I,D,FF,AFF"
+#define PID_LABELS "TimeUS,Des,Act,P,I,D,FF"
 #define PID_FMT    "Qffffff"
 #define PID_UNITS  "s------"
 #define PID_MULTS  "F------"