net: hns3: Support for dynamically assigning tx buffer to TC

This patch add support of dynamically assigning tx buffer to
TC when the TC is enabled.
It will save buffer for rx direction to avoid packet loss.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>