cxl/test: Add support for qos_class checking

cxl/test: Add support for qos_class checking

Set a fake qos_class to a unique value in order to do simple testing of
qos_class for root decoders and mem devs via user cxl_test. A mock
function is added to set the fake qos_class values for memory device
and overrides cxl_endpoint_parse_cdat() in cxl driver code.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20240206190431.1810289-5-dave.jiang@intel.com
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>