AP_NAvEKF3: use #define value for bad IMU hold time

libraries/AP_NavEKF3/AP_NavEKF3_PosVelFusion.cpp

@@ -693,7 +693,7 @@ void NavEKF3_core::FuseVelPosNED()
             } else {
                 goodIMUdata_ms = imuSampleTime_ms;
             }
-            if (imuSampleTime_ms - badIMUdata_ms < 10000) {
+            if (imuSampleTime_ms - badIMUdata_ms < BAD_IMU_DATA_HOLD_MS) {
                 badIMUdata = true;
             } else {
                 badIMUdata = false;

libraries/AP_NavEKF3/AP_NavEKF3_core.h

@@ -102,6 +102,9 @@
 // Number of milliseconds of bad IMU data before a reset to vertical position and velocity height sources is performed
 #define BAD_IMU_DATA_TIMEOUT_MS 1000
 
+// number of milliseconds the bad IMU data response settings will be held after the last bad IMU data is detected
+#define BAD_IMU_DATA_HOLD_MS 10000
+
 class NavEKF3_core : public NavEKF_core_common
 {
 public: