net: hns3: remove redundant memset when alloc buffer

HW will use packet length to write packets to buffer or read
packets from buffer. There is a redundant memset when alloc buffer,
the memset have no sense and will increase time-consuming.
This patch removes it.

Fixes: 76ad4f0e (net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC)

Signed-off-by: Lipeng <lipeng321@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>