boards: renesas: Rework rcar_salvator_xs doc

Rework renesas rcar_salvator_xs doc to meet what has
been done for the documentation of other rcar boards.
Also take advantage of these new boards documentation
features:
- zephyr:board
- zephyr:board-supported-hw
- zephyr:board-supported-runners

Signed-off-by: Aymeric Aillet <aymeric.aillet@iot.bzh>

boards/renesas/rcar_salvator_xs/doc/index.rst

@@ -1,7 +1,4 @@
-.. _rcar_salvator_xs:
-
-R-CAR Salvator XS M3 ARM CA57 (ARMv8)
-#####################################
+.. zephyr:board:: rcar_salvator_xs
 
 Overview
 ********
@@ -29,27 +26,12 @@ The R-Car M3-W includes:
 * CAN interface;
 * EtherAVB.
 
+Hardware capabilities for the Salvator-XS for can be found on the `eLinux Salvator-XS page`_.
+
 Supported Features
 ==================
-The Renesas rcar_salvator_xs board configuration supports the following
-hardware features:
-
-+-----------+------------------------------+--------------------------------+
-| Interface | Driver/components            | Support level                  |
-+===========+==============================+================================+
-| PINCTRL   | pinctrl                      |                                |
-+-----------+------------------------------+--------------------------------+
-| CLOCK     | clock_control                |                                |
-+-----------+------------------------------+--------------------------------+
-| UART      | uart                         | serial port-polling            |
-+-----------+------------------------------+--------------------------------+
-| MMC       | renesas_rcar_mmc             | DMA and SCC                    |
-+-----------+------------------------------+--------------------------------+
-
-Other hardware features have not been enabled yet for this board.
 
-The default configuration can be found in
-:zephyr_file:`boards/renesas/rcar_salvator_xs/rcar_salvator_xs_defconfig`
+.. zephyr:board-supported-hw::
 
 Programming and Debugging
 *************************