net: hns3: add support to config depth for tx|rx ring separately

This patch adds support to config depth for tx|rx ring separately
by ethtool command "-G".

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>