sensors: drivers: lsm6dsv16x: add SFLP FIFO support

Add the Sensor Fusion Low Power (SFLP) FIFO streaming capability,
using RTIO. The decode function is now aware of parsing following FIFO
tags:

    - LSM6DSV16X_SFLP_GAME_ROTATION_VECTOR_TAG
    - LSM6DSV16X_SFLP_GYROSCOPE_BIAS_TAG
    - LSM6DSV16X_SFLP_GRAVITY_VECTOR_TAG

To activate SFLP the user should put in DT the proper configuration.
For example, to activate a 60Hz SFLP FIFO batching rate of game rotation
vector, gravity vector and gbias components, the user should add in DT
the following:

  sflp-odr = <LSM6DSV16X_DT_SFLP_ODR_AT_60Hz>;
  sflp-fifo-enable = <LSM6DSV16X_DT_SFLP_FIFO_GAME_ROTATION_GRAVITY_GBIAS>;

Signed-off-by: Armando Visconti <armando.visconti@st.com>