net: hns3: modify functions of converting speed ability to ethtool link mode

The functions of converting speed ability to ethtool link mode just
support setting mac->supported currently, to reuse these functions to
set ethtool link mode for others(i.e. advertising), delete the argument
mac and add argument link_mode.

Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>