cxl/test: Add support for acpi extended linear cache

cxl/test: Add support for acpi extended linear cache

Add the mock wrappers for hmat_get_extended_linear_cache_size() in order
to emulate the ACPI helper function for the regions that are mock'd by
cxl_test.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Fabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>
Link: https://patch.msgid.link/20251117144611.903692-4-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>