dts: Include Kconfig.dts as optional source
dts: Include Kconfig.dts as optional source

Avoid build errors for platforms that do not support devicetree and
hence do not generate a Kconfig.dts.

Signed-off-by: Wolfgang Puffitsch <f148e6efbb74c70a1ee845a87fa7616913a99a4b@demant.com>

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