net: hns3: fix compile error when CONFIG_HNS3_DCB is not set

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

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Currently, CONFIG_HNS3_DCB is configed as y default, but in some
cases, it may not be set.

This patch fixes an compile error when CONFIG_HNS3_DCB is not set.

Signed-off-by: Junxin Chen <chenjunxin1@huawei.com>
Reviewed-by: Zhong Zhaohui <zhongzhaohui@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>