net: hns3: fix to correctly fetch l4 protocol outer header

This patch fixes the function being used to fetch L4
protocol outer header. Mistakenly skb_inner_transport_header
API was being used earlier.

Fixes: 76ad4f0e ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>