nfp: freeing the wrong variable

We accidentally free a NULL pointer and leak the pointer we want to
free.  Also you can tell from the label name what was intended.  :)

Fixes: abfcdc1d ("nfp: add a stats handler for flower offloads")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>