net: hns3: add default value for tc_size and tc_offset

This patch adds default value for tc_size and tc_offset, or it may
get random value and used later.

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>