net: hns: Remove redundant memset during buffer release

Because all members of desc_cb is assigned when xmit one package, so it
can delete in hnae_free_buffer, as follows:
        - "dma, priv, length, type" are assigned in fill_v2_desc.
        - "page_offset, reuse_flag, buf" are not used in tx direction.

Signed-off-by: lipeng <lipeng321@huawei.com>
Signed-off-by: Weiwei Deng <dengweiwei@huawei.com>
Reviewed-by: Yisen Zhuang <yisen.zhuang@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>