cxl/region: Quiet some dev_warn()s in extended linear cache setup

cxl/region: Quiet some dev_warn()s in extended linear cache setup

Extended Linear Cache (ELC) setup code emits a dev_warn(), "Extended
linear cache calculation failed." for issues found while setting up
the ELC.

For platforms without CONFIG_ACPI_HMAT, every auto region setup will
emit the warning because the default !ACPI_HMAT return value is
EOPNOTSUPP. Suppress it by skipping the warn for EOPNOTSUPP. Change
the EOPNOTSUPP in the actual ELC failure path to ENXIO.

Remove the check and enusing dev_warn() when region resource size is
NULL. The endpoint decoders hpa_range used to create the resource is
checked in init_hdm_decoder(), so it cannot be NULL here.

For good measure, add the rc value to the dev_warn(). It will either
be the -ENOENT returned by HMAT if the mem target is not found, or
the -ENXIO from the region driver calculation.

Reviewed-by: Li Ming <ming.li@zohomail.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20250306213700.2606304-1-alison.schofield@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>