net/hns3: fix RSS key length

net/hns3: fix RSS key length

When upper application calls the rte_eth_dev_rss_hash_conf_get API
function to get the RSS key parameters, the function should return the
RSS key length supported by the device. Otherwise, an error will occur
when the upper application needs to use the RSS key length supported
by this specified hardware for judgment and configure the specified
key into hardware.

For example, in the following scenario:
When users want to use their own RSS key, but the length of the key is
bigger than the one of the supported by hardware.

As a result, users need to get the RSS key length supported by hardware
according to the above API firstly, and then compare the actual obtained
RSS key length with the length of their own RSS key.

If the driver does not return the actual value, error may occur when
user calls the rte_eth_dev_rss_hash_update API function to configure
their own key into hardware.

Besides, this patch fixes the problem of stepping on memory when the RSS
key array configured by users are less than the RSS key length supported
by the driver at the same time.

Fixes: c37ca66f2b27 ("net/hns3: support RSS")
Cc: stable@dpdk.org
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>