net: hns3: Fixes API to fetch ethernet header length with kernel default

During the RX leg driver needs to fetch the ethernet header
length from the RX'ed Buffer Descriptor. Currently, proprietary
version hns3_nic_get_headlen is being used to fetch the header
length which uses l234info present in the Buffer Descriptor
which might not be valid for the first Buffer Descriptor if the
packet is spanning across multiple descriptors.
Kernel default eth_get_headlen API does the job correctly.

Fixes: 76ad4f0e

 ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Peng Li <lipeng321@huawei.com>
Reviewed-by: Yisen Zhuang <yisen.zhuang@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>