boards: silabs: xg24_rb4187c: Add SPI and I2C buses

Add DTS configuration for SPI and I2C buses on the board.
Make use of the new zephyr:board-supported-hw Sphinx directive to
automate the list of supported features in the board documentation.

Signed-off-by: Aksel Skauge Mellbye <aksel.mellbye@silabs.com>
3 files changed