amd64-9.0_RC1 panic: i915 related

["John D. Baker" <jdbaker%consolidated.net@localhost>]

My 82Q45-based workstation running a recent amd64-9.0_RC1 just sponaneously
panicked.  Processing the core dump with 'crash' shows:

  $ crash -N netbsd.0 -M netbsd.0.core             
  Crash version 9.0_RC1, image version 9.0_RC1.
  System panicked: trap
  Backtrace from time of crash is available.
  crash> bt
  _KERNEL_OPT_NAGR() at 0
  ?() at ffffb800f44c7000
  vpanic() at vpanic+0x169
  snprintf() at snprintf
  startlwp() at startlwp
  calltrap() at calltrap+0x11
  i915_capture_error_state() at i915_capture_error_state+0xef1
  i915_handle_error() at i915_handle_error+0x89
  linux_workqueue_thread() at linux_workqueue_thread+0x1a6


Nothing remarkable going on--I'd left it building evbmips-mips64el-current.
There was an "idle" firefox52 (as if firefox is ever idle).  Otherwise
the most active process was probably 'xlock'.

In case it's relevant, the Q45-based systems are broken with SNA in the
Xorg intel 2019 driver, so its using UXA with "TearFree" set to "false".

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