core/qdev: fix memleak in qdev_get_gpio_out_connector()

Fix a memory leak in qdev_get_gpio_out_connector().

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20200307030756.5913-1-pannengyuan@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

hw/core/qdev.c

@@ -557,7 +557,7 @@ void qdev_connect_gpio_out_named(DeviceState *dev, const char *name, int n,
 
 qemu_irq qdev_get_gpio_out_connector(DeviceState *dev, const char *name, int n)
 {
-    char *propname = g_strdup_printf("%s[%d]",
+    g_autofree char *propname = g_strdup_printf("%s[%d]",
                                      name ? name : "unnamed-gpio-out", n);
 
     qemu_irq ret = (qemu_irq)object_property_get_link(OBJECT(dev), propname,