net: hns3: Fixes the missing u64_stats_fetch_begin_irq in 64-bit stats fetch

This patch fixes the missing u64_stats_fetch_begin_irq() while trying to
atomically do 64-bit RX/TX fetch. We did not get any error during test
as our SoC is 64-bit so all of these seq/lock operations results in NOOP.

As such, this seq lock supports has been added for the sake of completion
if this code ever runs on 32-bit platform and we are trying to do 64-bit
stats fetch.

Fixes: 76ad4f0e ("net: hns3: Add support of HNS3 Ethernet Driver for
hip08 SoC")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>