tools/testing/cxl: Use named effects for the Command Effect Log

As more emulated mailbox commands are added to cxl_test, it is a pain
point to look up command effect numbers for each effect. Replace the
bare numbers in the mock driver with an enum that lists all possible
effects.

Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Cc: Russ Weight <russell.h.weight@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ben Widawsky <bwidawsk@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/20230602-vv-fw_update-v4-3-c6265bd7343b@intel.com


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