net: hns3: fix setting wrong tx_timeout value issue

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7OL9R


CVE: NA

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When user set tx_timeout, hns3 driver should set tx_timeout * HZ to
ndev->watchdog_timeo but tx_timeout.

So, change it to be correct.

Fixes: dd347d0d (net: hns3: add support modified tx timeout)
Signed-off-by: Hao Chen <chenhao418@huawei.com>
Signed-off-by: Jijie Shao <shaojijie@huawei.com>