cxl/acpi: Make the XOR calculations available for testing

cxl/acpi: Make the XOR calculations available for testing

In preparation for adding a test module that can exercise the address
translation functions performed by the CXL Driver, refactor the XOR
implementation like this:

- Extract the core calculation into a standalone helper function,
- Export the new function for use by test module cxl_translate only,
- Enhance the parameter validation since this new function will be
  called from a test module with no guarantee of valid parameters,
- Move the define of struct cxl_cxims_data to cxl.h so the test module
  can build xormaps.

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>