dax/bus: Upgrade resource conflict message to dev_err() in alloc_dax_region()

The dax_region resource conflict in alloc_dax_region() indicates a
serious configuration problem — two subsystems (e.g. dax_hmem and
dax_cxl) are attempting to register overlapping address ranges. This is
not a transient or debug-level condition; it represents a genuine
resource conflict that an administrator needs to be aware of.

Promote the log level from dev_dbg() to dev_err() so that the conflict
is visible by default without requiring dynamic debug to be enabled.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/linux-cxl/69c1a8d1c0fa9_7ee3100a1@dwillia2-mobl4.notmuch/
Signed-off-by: Tomasz Wolski <tomasz.wolski@fujitsu.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Richard Cheng <icheng@nvidia.com>
Link: https://patch.msgid.link/20260528064546.23362-1-tomasz.wolski@fujitsu.com
Signed-off-by: Alison Schofield <alison.schofield@intel.com>

Author: twlski

drivers/dax/bus.c

@@ -670,7 +670,7 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 
 	rc = request_resource(&dax_regions, &dax_region->res);
 	if (rc) {
-		dev_dbg(parent, "dax_region resource conflict for %pR\n",
+		dev_err(parent, "dax_region resource conflict for %pR\n",
 			&dax_region->res);
 		goto err_res;
 	}