net: hns3: optimize local variable of hclge_set_loopback() function

driver inclusion
category: cleanup
bugzilla: NA
CVE: NA

This patch deletes redundant initialization of variable ret, and
modify the varibale name "value" to "switch_param" for clearer
meaning.

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