net: hns3: code optimization for debugfs related to "dump reg"

For making the code more readable, this patch uses a array to
keep the information about the dumping register, and then uses
it to parse the parameter cmd_buf which passing into
hclge_dbg_dump_reg_cmd().

Also replaces parameter "base" of kstrtouint with 0 in the
hclge_dbg_dump_reg_common(), which makes it more flexible.

Signed-off-by: Zhongzhu Liu <liuzhongzhu@huawei.com>
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>