net: hns3: fix a bug when alloc new buffer

net: hns3: fix a bug when alloc new buffer

[ Upstream commit b9077428ec5569aacb2952d8a2ffb51c8988d3c2 ]

When alloce new buffer to HW, should unmap the old buffer first.
This old code map the old buffer but not unmap the old buffer,
this patch fixes it.

Fixes: 76ad4f0 (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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>