net: hns3: fix show wrong state when add existing uc mac address

Currently, if function adds an existing unicast mac address, eventhough
driver will not add this address into hardware, but it will return 0 in
function hclge_add_uc_addr_common(). It will cause the state of this
unicast mac address is ACTIVE in driver, but it should be in TO-ADD state.

To fix this problem, function hclge_add_uc_addr_common() returns -EEXIST
if mac address is existing, and delete two error log to avoid printing
them all the time after this modification.

Fixes: 72110b56 ("net: hns3: return 0 and print warning when hit duplicate MAC")
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>