nand: put it into the 'storage' category

The category of the nand device is not set, put it into the 'storage'
category.

Signed-off-by: Gan Qixin <ganqixin@huawei.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201112125824.763182-4-ganqixin@huawei.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/block/nand.c

@@ -449,6 +449,7 @@ static void nand_class_init(ObjectClass *klass, void *data)
     dc->reset = nand_reset;
     dc->vmsd = &vmstate_nand;
     device_class_set_props(dc, nand_properties);
+    set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
 }
 
 static const TypeInfo nand_info = {