drm/i915: undefined STOP_MACHINE

[Valentin Rothberg]

Dear Chris,

your commit 9f267eb8d2ea ("drm/i915: Stop the machine whilst capturing
the GPU crash dump") has popped up in today's linux-next and adds a
select from DRM_I915 on STOP_MACHINE, which is not defined anywhere in
Kconfig.

STOP_MACHINE has been removed a while ago (see
https://lkml.org/lkml/2015/11/19/133).  I assume that HOTPLUG_CPU
could be used?

I detected the issue with scripts/checkkconfigsymbols.py by diffing
yesterday's and today's linux-next.

Best regards,
 Valentin