west: Fix defining modules without a module.yml

It is supported to have a zephyr module that does not have a
module.yml, but zephyr_module.py does not support it and will drop
such modules.

To fix this we add support in zephyr_module.py.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>
diff --git a/scripts/zephyr_module.py b/scripts/zephyr_module.py
index 264ba8d..5bde894 100755
--- a/scripts/zephyr_module.py
+++ b/scripts/zephyr_module.py
@@ -79,6 +79,9 @@
     module_path = PurePath(module)
     module_yml = module_path.joinpath('zephyr/module.yml')
 
+    # The input is a module if zephyr/module.yml is a valid yaml file
+    # or if both zephyr/CMakeLists.txt and zephyr/Kconfig are present.
+
     if Path(module_yml).is_file():
         with Path(module_yml).open('r') as f:
             meta = yaml.safe_load(f.read())
@@ -92,6 +95,10 @@
 
         return meta
 
+    if Path(module_path.joinpath('zephyr/CMakeLists.txt')).is_file() and \
+       Path(module_path.joinpath('zephyr/Kconfig')).is_file():
+        return {'build': {'cmake': 'zephyr', 'kconfig': 'zephyr/Kconfig'}}
+
     return None