net: hns3: remove the way to set tx spare buf via module parameter

The way to set tx spare buf via module parameter is not such
convenient as the way to set it via ethtool.

So,remove the way to set tx spare buf via module parameter.

Signed-off-by: Hao Chen <chenhao288@hisilicon.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>