monitor: Better express monitor_read()'s opaque arg is of Monitor type monitor_read() is a IOReadHandler handler, called by qemu_chr_fe_set_handlers() with a Monitor* opaque argument. Signed-off-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20260812211708.92824-20-philmd@oss.qualcomm.com>