net: hns3: divide shared buffer between TC

Currently hardware may have not enough buffer to receive packet
when it has used more than two MPS(maximum packet size) of
buffer, but there are still a lot of shared buffer left unused
when TC num is small.

This patch divides shared buffer to be used between TC when
the port supports DCB, and adjusts the waterline and threshold
according to user manual for the port that does not support
DCB.

This patch also change hclge_get_tc_num's return type to u32
to avoid signed-unsigned mix with divide.

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