port-alpha/56434: alpha testbed installs fail with cmdide errors

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         56434
>Category:       port-alpha
>Synopsis:       alpha testbed installs fail with cmdide errors
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    port-alpha-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Oct 02 11:20:00 +0000 2021
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2021.09.25.08.54.31
>Organization:
  
>Environment:
System: NetBSD
Architecture: alpha
Machine: alpha
>Description:

The TNF alpha testbed is now consistently failing at the install stage,
with errors like this one:

  cmdide0:0:0: lost interrupt
  [  21.1241301]  type: ata tc_bcount: 8192 tc_skip: 0
  cmdide0:0:0: bus-master DMA error: missing interrupt, status=0x60
  [  21.1241301] wd0: excessive DMA errors - 4 in last 11 transfers
  [  21.1241301] wd0c: DMA error reading fsbn 128 of 128-143 (wd0 bn 128; cn 0 tn 2 sn 2), xfer 38, retry 0

My own testbed behaves the same way.  Logs are at:

  http://releng.netbsd.org/b5reports/alpha/commits-2021.09.html#2021.09.25.08.54.31
  https://www.gson.org/netbsd/bugs/build/alpha/commits-2021.09.html#2021.09.25.08.54.31

On both testbeds, the problem appears to have started with maya's
commit introducing the gpufw set, but I don't see any obvious
connection between the commit and the error.

>How-To-Repeat:

Install misc/py-anita and emulators/qemu from pkgsrc and run

  anita install http://nycdn.netbsd.org/pub/NetBSD-daily/HEAD/latest/alpha/

>Fix: