net: hns3: add support config dscp map to tc

This patch add support config dscp map to tc by implementing ieee_setapp
and ieee_delapp of struct dcbnl_rtnl_ops. Driver will convert mapping
relationship from dscp-prio to dscp-tc.

Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>