The get_frame_count() API must return the number of frames in FIFO
for a given channel type, and not the total number of generic FIFO
frames. This API may be also re-used in the decoder routine when
the timestamp baseline is adjusted.

Signed-off-by: Armando Visconti <[email protected]>

Add sample to read from up to 10 FIFO streaming devices, using the
sensor_stream() API and the RTIO framework:
    https://docs.zephyrproject.org/latest/services/rtio/index.html

The devices has to be aliased as streamN (0 <= N <= 9) in DT, and
will be instantiated using SENSOR_DT_STREAM_IODEV() macro.

Currently the sample gets/prints data on SENSOR_TRIG_FIFO_WATERMARK
trigger basis for the following sensor channels:

    - SENSOR_CHAN_ACCEL_XYZ
    - SENSOR_CHAN_GYRO_XYZ
    - SENSOR_CHAN_DIE_TEMP

Signed-off-by: Armando Visconti <[email protected]>