IMU: move _sensor_cal to general IMU class

this makes it available both in shim and INS subclasses

libraries/AP_IMU/AP_IMU_INS.cpp

@@ -21,11 +21,6 @@
 
 #include "AP_IMU_INS.h"
 
-const AP_Param::GroupInfo AP_IMU_INS::var_info[] PROGMEM = {
-    AP_GROUPINFO("CAL", 0, AP_IMU_INS, _sensor_cal),
-    AP_GROUPEND
-};
-
 void
 AP_IMU_INS::init( Start_style style,
                   void (*delay_cb)(unsigned long t),

libraries/AP_IMU/AP_IMU_INS.h

@@ -64,11 +64,8 @@ public:
 	virtual void		ay(const float v)		{ _sensor_cal[4] = v; }
 	virtual void		az(const float v)		{ _sensor_cal[5] = v; }
 
-    static const struct AP_Param::GroupInfo var_info[];
-
 private:
     AP_InertialSensor   *_ins;          ///< INS provides an axis and unit correct sensor source.
-    AP_Vector6f         _sensor_cal;    ///< Calibrated sensor offsets
 
     virtual void        _init_accel(void (*delay_cb)(unsigned long t),
                                     void (*flash_leds_cb)(bool on) = NULL);  ///< no-save implementation

libraries/AP_IMU/IMU.cpp

@@ -1,6 +1,13 @@
 
 #include "IMU.h"
 
+// this allows the sensor calibration to be saved to EEPROM
+const AP_Param::GroupInfo IMU::var_info[] PROGMEM = {
+    AP_GROUPINFO("CAL", 0, IMU, _sensor_cal),
+    AP_GROUPEND
+};
+
+
 /* Empty implementations for the IMU functions.
  * Although these will never be used, in certain situations with
  * optimizations turned off, having empty implementations in an object

libraries/AP_IMU/IMU.h

@@ -104,7 +104,12 @@ public:
 	virtual void		ay(const float v);
 	virtual void		az(const float v);
 
+	static const struct AP_Param::GroupInfo var_info[];
+
 protected:
+
+    AP_Vector6f         _sensor_cal;    ///< Calibrated sensor offsets
+
 	/// Most recent accelerometer reading obtained by ::update
 	Vector3f		_accel;
 	Vector3f		_accel_filtered;