boards: define Arduino SPI standard chip select for Nordic boards

Prepare for a day when all boards specify the chip select in the bus
devicetree node by making sure that the devicetree node associated
with arduino_spi uses the standard D10 pin from the arduino header as
the cs-gpios property value.

Also update the arduino tags in the board yaml files.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
7 files changed