AP_NavEKF2: move KH array inside for the remaining user

Not used by AP_NavEKF3.

libraries/AP_NavEKF2/AP_NavEKF2_core.cpp

@@ -30,6 +30,8 @@ extern const AP_HAL::HAL& hal;
  */
 #define ENABLE_EKF_TIMING 0
 
+NavEKF2_core::Matrix24 NavEKF2_core::KH;
+
 // constructor
 NavEKF2_core::NavEKF2_core(NavEKF2 *_frontend) :
     dal(AP::dal()),
@@ -543,6 +545,9 @@ void NavEKF2_core::UpdateFilter(bool predict)
 #endif
 
     fill_scratch_variables();
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+    fill_nanf(&KH[0][0], sizeof(KH)/sizeof(ftype)); // see fill_scratch_variables()
+#endif
 
     // TODO - in-flight restart method
 

libraries/AP_NavEKF2/AP_NavEKF2_core.h

@@ -788,6 +788,8 @@ private:
     static const uint32_t FLOW_BUFFER_LENGTH = 15;
     static const uint32_t EXTNAV_BUFFER_LENGTH = 15;
 
+    static Matrix24 KH;             // intermediate result used for covariance updates
+
     // Variables
     bool statesInitialised;         // boolean true when filter states have been initialised
     bool magHealth;                 // boolean true if magnetometer has passed innovation consistency check