boards: bytesatwork: adopt new zephyr:board directive and role

This updates the documentation of all the bytesatwork boards to use
the new `zephyr:board::` directive.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

boards/bytesatwork/bytesensi_l/doc/index.rst

@@ -1,7 +1,4 @@
-.. _bytesensi_l:
+.. zephyr:board:: bytesensi_l
-
-bytesatwork byteSENSI-L
-#######################
 
 Overview
 ********
@@ -9,11 +6,6 @@ Overview
 The byteSENSI-L is a fun LoRa device based on nRF52 MCU that integrates many
 sensors.
 
-.. image:: img/byteSENSI-L.jpg
-   :width: 800px
-   :align: center
-   :alt: byteSENSI-L
-
 Hardware
 ********