net: hns3: add support handling tx dhcp packets for ROH

driver inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6BSMN



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For ROH distributed scenario, EID is allocated by DHCP mode.
Driver needs to convert the origin MAC address to EID format,
and updates the destination MAC, chaddr and client id(if exists)
when transmit DHCP packets. Meantime, the chaddr field should
follow the source mac address, in order to make the dhcp
server reply to the right client. For the payload of
dhcp packet changed, so the checksum of L4 should be
calculated too.

Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Ke Chen <chenke54@huawei.com>