acpi/nfit: rely on mce->misc to determine poison granularity

nfit_handle_mec() hardcode poison granularity at L1_CACHE_BYTES.
Instead, let the driver rely on mce->misc register to determine
the poison granularity.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Link: https://lore.kernel.org/r/20220422224508.440670-2-jane.chu@oracle.com


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