tools/testing/cxl: Remove unused @cxlds argument

In preparation for plumbing a 'struct cxl_memdev_state' as a superset of
a 'struct cxl_dev_state' cleanup the usage of @cxlds in the unit test
infrastructure.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/168679258640.3436160.7641308222525246728.stgit@dwillia2-xfh.jf.intel.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>