net: hns3: always assume no drop TC for performance reason

Currently RX shared buffer' threshold size for speific TC is
set to smaller value when the TC's PFC is not enabled, which may
cause performance problem because hardware may not have enough
hardware buffer when PFC is not enabled.

This patch sets the same threshold size for all TC no matter if
the specific TC's PFC is enabled.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
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>