net: hns3: return 0 and print warning when hit duplicate MAC

When set 2 same MAC to different function of one port, IMP
will return error as the later one may modify the origin one.
This will cause bond fail for 2 VFs of one port.

Driver just print warning and return 0 with this patch, so
if set same MAC address, it will return 0 but do not really
configure HW.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>