CI: allow non-standard signature

Make allow to use non-standard signature such as 'Co-authored-by:'.

Signed-off-by: TOKITA Hiroshi <[email protected]>

Author: soburi

.github/workflows/checkpatch.yml

@@ -25,6 +25,7 @@ jobs:
       with:
         ref: ${{ github.event.pull_request.head.sha }}
         fetch-depth: ${{ env.PR_FETCH_DEPTH }}
+        args: --ignore=NON_STANDARD_SIGNATURE
     - name: Run checkpatch review
       uses: webispy/checkpatch-action@v9