fixed broken PID

sidservo.h

@@ -136,10 +136,10 @@ typedef struct{
 } extradata_t;
 
 typedef enum{
-    AXIS_STOPPED,
-    AXIS_SLEWING,
-    AXIS_POINTING,
-    AXIS_GUIDING,
+    AXIS_STOPPED,   // stop
+    AXIS_SLEWING,   // go to target with maximal speed
+    AXIS_POINTING,  // axis is in pointing zone, use PID
+    AXIS_GUIDING,   // near target
     AXIS_ERROR,
 } axis_status_t;