edtlib: Remove unreachable code

This fixes the following error reported by
./scripts/ci/check_compliance.py:

> 1 checks failed
> ERROR   : Test Pylint failed:
> W0101:Unreachable code (unreachable)
> File:scripts/dts/python-devicetree/src/devicetree/edtlib.py
> Line:2271
> Column:16
>
> Complete results in compliance.xml

Signed-off-by: Reto Schneider <reto.schneider@husqvarnagroup.com>