macio: Tidy up error handling in macio_newworld_realize()

macio_newworld_realize() effectively ignores ns->gpio realization
errors, leaking the Error object.  Fortunately, macio_gpio_realize()
can't actually fail.  Tidy up.

Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200707160613.848843-6-armbru@redhat.com>

hw/misc/macio/macio.c

@@ -334,7 +334,9 @@ static void macio_newworld_realize(PCIDevice *d, Error **errp)
                                  &error_abort);
         memory_region_add_subregion(&s->bar, 0x50,
                                     sysbus_mmio_get_region(sysbus_dev, 0));
-        qdev_realize(DEVICE(&ns->gpio), BUS(&s->macio_bus), &err);
+        if (!qdev_realize(DEVICE(&ns->gpio), BUS(&s->macio_bus), errp)) {
+            return;
+        }
 
         /* PMU */
         object_initialize_child(OBJECT(s), "pmu", &s->pmu, TYPE_VIA_PMU);