hw/nubus/nubus-device: Fix memory leak in nubus_device_realize

hw/nubus/nubus-device: Fix memory leak in nubus_device_realize

Local variable "name" is allocated through strdup_printf and should be
freed with g_free() to avoid memory leak.

Fixes: 3616f424 ("nubus-device: add romfile property for loading declaration ROMs")
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20221222172915.671597-1-mcascell@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>