qom: Have class_init() take a const data argument

Mechanical change using gsed, then style manually adapted
to pass checkpatch.pl script.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20250424194905.82506-4-philmd@linaro.org>
diff --git a/io/channel-buffer.c b/io/channel-buffer.c
index 8096180..189fa67 100644
--- a/io/channel-buffer.c
+++ b/io/channel-buffer.c
@@ -225,7 +225,7 @@
 
 
 static void qio_channel_buffer_class_init(ObjectClass *klass,
-                                          void *class_data G_GNUC_UNUSED)
+                                          const void *class_data G_GNUC_UNUSED)
 {
     QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);