mpu9250: lowPowerAccelOnly may be called from LP_ACCEL to change update rate

    src: [STANDBY, LP_ACCEL, ACCEL, GYRO, MAGNET, NINEAXIS]

    dst: SLEEP

  lowPowerAccelOnly:

    src: [SLEEP, STANDBY, NINEAXIS, ACCEL, GYRO, MAGNET]

    src: [SLEEP, STANDBY, NINEAXIS, LP_ACCEL, ACCEL, GYRO, MAGNET]

    dst: LP_ACCEL

    arguments:

    - name: rate