net: hns3: add unlikely for error check

The first bd of a packet is invalid and invalid ring head for tx
IRQ is not offen, they may occur when there is error,
Add unlikely for error check branch is better for performance.

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