net/mlx4_en: do not ignore autoneg in mlx4_en_set_pauseparam()

commit 278d436a476f69fc95d5c82bf61b6c2d02f4d44e upstream.

The driver does not support pause autonegotiation so it should return
-EINVAL when the function is called with non-zero autoneg.

Cc: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>