AP_InertialSensor: fixed LSM303D registered sample rate

we are running the LSM303D at 1600Hz, and are sampling it at 1kHz. We
need to tell the AP_InertialSensor layer that samples will arrive at 1kHz

libraries/AP_InertialSensor/AP_InertialSensor_LSM9DS0.cpp

@@ -523,7 +523,7 @@ fail_whoami:
 void AP_InertialSensor_LSM9DS0::start(void)
 {
     _gyro_instance = _imu.register_gyro(760, _dev_gyro->get_bus_id_devtype(DEVTYPE_GYR_L3GD20));
-    _accel_instance = _imu.register_accel(800, _dev_accel->get_bus_id_devtype(DEVTYPE_ACC_LSM303D));
+    _accel_instance = _imu.register_accel(1000, _dev_accel->get_bus_id_devtype(DEVTYPE_ACC_LSM303D));
 
     if (whoami_g == LSM9DS0_G_WHOAMI_H) {
         set_gyro_orientation(_gyro_instance, _rotation_gH);