net: hns3: remove redundant assignment of l2_hdr to itself

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

The pointer l2_hdr is being assigned to itself, this is redundant
and can be removed.

fix from community.

Feature or Bugfix:Bugfix

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