netconsole: Warn if MAX_USERDATA_ITEMS limit is exceeded

netconsole configfs helpers doesn't allow the creation of more than
MAX_USERDATA_ITEMS items.

Add a warning when netconsole userdata update function attempts sees
more than MAX_USERDATA_ITEMS entries.

Replace silent ignore mechanism with WARN_ON_ONCE() to highlight
potential misuse during development and debugging.

Signed-off-by: Breno Leitao <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: leitao

drivers/net/netconsole.c

@@ -730,7 +730,7 @@ static void update_userdata(struct netconsole_target *nt)
 		struct userdatum *udm_item;
 		struct config_item *item;
 
-		if (child_count >= MAX_USERDATA_ITEMS)
+		if (WARN_ON_ONCE(child_count >= MAX_USERDATA_ITEMS))
 			break;
 		child_count++;