cxl/region: Simplify cxl_region_nid()

The node ID of the region can be gotten via resource start address
directly.  This simplifies the implementation of cxl_region_nid().
Signed-off-by: Huang Ying <ying.huang@intel.com>
Suggested-by: Alison Schofield <alison.schofield@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://patch.msgid.link/20240618084639.1419629-4-ying.huang@intel.comSigned-off-by: Dave Jiang <dave.jiang@intel.com>

drivers/cxl/core/region.c

@@ -2309,15 +2309,13 @@ static bool cxl_region_update_coordinates(struct cxl_region *cxlr, int nid)
 static int cxl_region_nid(struct cxl_region *cxlr)
 {
 	struct cxl_region_params *p = &cxlr->params;
-	struct cxl_endpoint_decoder *cxled;
-	struct cxl_decoder *cxld;
+	struct resource *res;
 
 	guard(rwsem_read)(&cxl_region_rwsem);
-	cxled = p->targets[0];
-	if (!cxled)
+	res = p->res;
+	if (!res)
 		return NUMA_NO_NODE;
-	cxld = &cxled->cxld;
-	return phys_to_target_node(cxld->hpa_range.start);
+	return phys_to_target_node(res->start);
 }
 
 static int cxl_region_perf_attrs_callback(struct notifier_block *nb,