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 <[email protected]>
Link: https://lore.kernel.org/linux-cxl/[email protected]/
Signed-off-by: Tomasz Wolski <[email protected]>
Reviewed-by: Alison Schofield <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
Reviewed-by: Richard Cheng <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Alison Schofield <[email protected]>

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;
 	}