net: hns3: Check for allocation failure

We should return -ENOMEM if the kcalloc() fails.

Fixes: d174ea75

 ("net: hns3: add statistics for PFC frames and MAC control frame")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>