Pktdrv calculates wrong packet length

[JayFoxRox]

Formula for packet length should probably be this (based on disassembly):

unsigned int length = flag & 0xFFFF;
if (flag & NV_RX_SUBSTRACT1) {
  assert(length > 0);
  length--;
}

(Code in XQEMU and Cxbx-R downstream should be checked, too)

[Teufelchen1]

FTR: @thrimbor is working on a replacement for pktdrv that will likely fix this issue.

[JayFoxRox]

This was supposed to be closed by #611

Closed.