zephyr: update devicetree py package lib files include path in assembly

This PR updates the path to the devicetree python package lib files according to the Zephyr PR
zephyrproject-rtos#33746 which moved the devicetree lib files.

Old path: ZEPHYR_BASE/scripts/dts/
New path: ZEPHYR_BASE/scripts/dts/python-devicetree/src/devicetree/

Signed-off-by: Carl-Johan Landin <carl-johan.landin@endian.se>