net: hns3: fix for dereferencing before null checking

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

The netdev is dereferenced before null checking in the function
hns3_setup_tc.

This patch moves the dereferencing after the null checking.

Fixes: 76ad4f0e ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")

Feature or Bugfix:Bugfix

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Reviewed-by: liuyonglong <liuyonglong@huawei.com>
Reviewed-by: lipeng <lipeng321@huawei.com>
Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>