MAINTAINERS: add file glob for cmsis_6

Add modules/cmsis_6 to the list of files under CMSIS_6.

Signed-off-by: Benjamin Cabé <[email protected]>

Author: kartben

MAINTAINERS.yml

@@ -5191,7 +5191,8 @@ West:
   collaborators:
     - tomi-font
     - ithinuel
-  files: []
+  files:
+    - modules/cmsis_6/
   labels:
     - "area: CMSIS_6"