net: hns3: remediate a potential overflow risk of bd_num_list

The array size of bd_num_list is a fixed value, it may have potential
overflow risk when array size of hclge_dfx_bd_offset_list is greater
than that fixed value. So modify bd_num_list as a pointer and allocate
memory for it according to array size of hclge_dfx_bd_offset_list.

Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>