nfp: replace -ENOTSUPP with -EOPNOTSUPP

As Or points out in commit 423b3aec ("net/mlx4: Change ENOTSUPP
to EOPNOTSUPP"), ENOTSUPP is NFS specific error.  Replace it with
EOPNOTSUPP.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>