hw/watchdog/wdt_i6300esb: Use DEVICE() macro to access DeviceState.qdev

Rather than looking inside the definition of a DeviceState with
"s->qdev", use the QOM prefered style: "DEVICE(s)".

This patch was generated using the following Coccinelle script:

    // Use DEVICE() macros to access DeviceState.qdev
    @use_device_macro_to_access_qdev@
    expression obj;
    identifier dev;
    @@
    -&obj->dev.qdev
    +DEVICE(obj)
Suggested-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NLaurent Vivier <laurent@vivier.eu>
Message-Id: <20190528164020.32250-11-philmd@redhat.com>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>

hw/watchdog/wdt_i6300esb.c

@@ -200,7 +200,7 @@ static void i6300esb_timer_expired(void *vp)
         if (d->reboot_enabled) {
             d->previous_reboot_flag = 1;
             watchdog_perform_action(); /* This reboots, exits, etc */
-            i6300esb_reset(&d->dev.qdev);
+            i6300esb_reset(DEVICE(d));
         }
 
         /* In "free running mode" we start stage 1 again. */