drm/i915/gt: Warn CI about an unrecoverable wedge

If we have a wedged GPU that we need to recover, but fail, add a taint
for CI to pickup and schedule a reboot.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Petri Latvala <petri.latvala@intel.com>
Reviewed-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191002160034.5121-1-chris@chris-wilson.co.uk