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/chardev/char-stdio.c b/chardev/char-stdio.c
index b960ddd..48db8d2 100644
--- a/chardev/char-stdio.c
+++ b/chardev/char-stdio.c
@@ -136,7 +136,7 @@
     stdio->signal = qemu_opt_get_bool(opts, "signal", true);
 }
 
-static void char_stdio_class_init(ObjectClass *oc, void *data)
+static void char_stdio_class_init(ObjectClass *oc, const void *data)
 {
     ChardevClass *cc = CHARDEV_CLASS(oc);