boards: arm: seeeduino_xiao: fix vendor prefix
boards: arm: seeeduino_xiao: fix vendor prefix

Use "seeed" instead of "seeedstudio", as the former is registered in
`dts/bindings/vendor-prefixes.txt`.

Signed-off-by: Marcin Niestroj <63506c06cfbc47ace147db1702f6e751f5ac2132@emb.dev>

galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr