* Bump the number of Rx descriptors from 128 to 256.
* Don't use a sliding Tx interrupt window. Instead, just do reap-behind
when we have <= 1/8 of our available descriptors in wm_start().
* Don't use Tx Queue Empty interrupts, and always set the Tx Interrupt
Delay bit in the Tx descriptor.
* In wm_intr(), always call wm_rxintr() and wm_txintr(), regardless of
their respective ISR bits being set. We're here, might as well do some
work.
* Adjust the Tx and Rx interrupt delay timer values. New values from
Intel's driver for FreeBSD via Allen Briggs.
With these changes, NetBSD can sustain > 900Mb/s userland to userland
*without* using TCP checksum offload using Intel PRO/1000 XT cards.