console: Don't notify user space when unregister non-listed console

If console is not on the list then there is nothing for us to do
and sysfs notify is pointless.

Note, that nr_ext_console_drivers is being changed only for listed
consoles.

Suggested-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Link: http://lkml.kernel.org/r/20200203133130.11591-6-andriy.shevchenko@linux.intel.com
To: linux-kernel@vger.kernel.org
To: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>

kernel/printk/printk.c

@@ -2836,7 +2836,10 @@ int unregister_console(struct console *console)
 		}
 	}
 
-	if (!res && (console->flags & CON_EXTENDED))
+	if (res)
+		goto out_disable_unlock;
+
+	if (console->flags & CON_EXTENDED)
 		nr_ext_console_drivers--;
 
 	/*
@@ -2849,6 +2852,13 @@ int unregister_console(struct console *console)
 	console->flags &= ~CON_ENABLED;
 	console_unlock();
 	console_sysfs_notify();
+
+	return res;
+
+out_disable_unlock:
+	console->flags &= ~CON_ENABLED;
+	console_unlock();
+
 	return res;
 }
 EXPORT_SYMBOL(unregister_console);