AP_AHRS: constify getLastYawResetAngle

libraries/AP_AHRS/AP_AHRS.h

@@ -388,8 +388,8 @@ public:
 
     // return the amount of yaw angle change due to the last yaw angle reset in radians
     // returns the time of the last yaw angle reset or 0 if no reset has ever occurred
-    virtual uint32_t getLastYawResetAngle(float &yawAng) {
-        return false;
+    virtual uint32_t getLastYawResetAngle(float &yawAng) const {
+        return 0;
     };
 
     // return the amount of NE position change in metres due to the last reset

libraries/AP_AHRS/AP_AHRS_NavEKF.cpp

@@ -729,7 +729,7 @@ const char *AP_AHRS_NavEKF::prearm_failure_reason(void) const
 
 // return the amount of yaw angle change due to the last yaw angle reset in radians
 // returns the time of the last yaw angle reset or 0 if no reset has ever occurred
-uint32_t AP_AHRS_NavEKF::getLastYawResetAngle(float &yawAng)
+uint32_t AP_AHRS_NavEKF::getLastYawResetAngle(float &yawAng) const
 {
     switch (ekf_type()) {
     case 1:
@@ -737,7 +737,7 @@ uint32_t AP_AHRS_NavEKF::getLastYawResetAngle(float &yawAng)
     case 2:
         return EKF2.getLastYawResetAngle(yawAng);
     }
-    return false;
+    return 0;
 }
 
 // return the amount of NE position change in metres due to the last reset

libraries/AP_AHRS/AP_AHRS_NavEKF.h

@@ -165,7 +165,7 @@ public:
 
     // return the amount of yaw angle change due to the last yaw angle reset in radians
     // returns the time of the last yaw angle reset or 0 if no reset has ever occurred
-    uint32_t getLastYawResetAngle(float &yawAng);
+    uint32_t getLastYawResetAngle(float &yawAng) const;
 
     // return the amount of NE position change in metres due to the last reset
     // returns the time of the last reset or 0 if no reset has ever occurred