By default, lazy_tx_credit_flush will process packets by batch of 15
packets or less. With this change, batches or 64 packets are directly
processed. Under high load, this prevents to fill up completely the TX
ring and then to flush it entirely.
Submitted by: Marc De La Gueronniere <firstname.lastname@example.org>
MFC after: 1 week
Sponsored by: Verisign, Inc.