netxen: Error return off by one in 'netxen_nic_set_pauseparam()'.

There are 'NETXEN_NIU_MAX_GBE_PORTS'  GBE ports. Port indexing starts
from zero.
Hence we should also return error for "port == NETXEN_NIU_MAX_GBE_PORTS"

Signed-off-by: Santosh Nayak <santoshprasadnayak@gmail.com>