sensors: add new channels to support sensor fusion

Add three new channels and relative data:

    - SENSOR_CHAN_GAME_ROTATION_VECTOR

      The "game rotation vector" reports the four components x/y/z/w
      (quaternions) of the unit vector representing a 3D spatial
      rotation or orientation.

    - SENSOR_CHAN_GRAVITY_VECTOR

      The "gravity vector" reports the three axis x/y/z of the gravity
      vector separated from the linear acceleration components.
      The measurement unit is m/s^2.

    - SENSOR_CHAN_GBIAS_XYZ

      The "gbias" reports the gyroscope offset x/y/z components.
      The measurement unit is radians/s.

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