net: hns3: reduce resources use in kdump kernel

When the kdump kernel started, the HNS3 driver fail to register:
[14.753340] hns3 0000:7d:00.0: Alloc umv space failed, want 512, get 0
[14.795034] hns3 0000:7d:00.0: add uc mac address fail, ret =-22.

By default, the HNS3 driver will use about 512M memory, but
usually the reserved memory of kdump kernel is 576M, so the HNS3
driver fail to register. This patch reduces the memory use in
kdump kernel to about 16M.

And when the kdump kernel starts, we must clear ucast mac address
first to avoid add fail.

Signed-off-by: Yonglong Liu <liuyonglong@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>