net: hns3: modify definition location of struct hclge_mac_ethertype_idx_rd_cmd

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

--------------------------------------------

This patch just modifies definition location of struct
hclge_mac_ethertype_idx_rd_cmd to sync code with linux mainline.

Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: shenhao <shenhao21@huawei.com>
Reviewed-by: Zhong Zhaohui <zhongzhaohui@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>