hwdb: add missing Group()

This fixes the following warning:
```
parse_hwdb.py:120: UserWarning: warn_ungrouped_named_tokens_in_collection: setting results name 'SETTINGS*' on And expression collides with 'HZ' on contained expression
  dpi_setting = (Optional('*')('DEFAULT') + INTEGER('DPI') + Suppress('@') + INTEGER('HZ'))('SETTINGS*')
```

Not sure about for the mount_matrix, but LGTM.com warns in that line,
and, adding Group() does not change the parse result.