drm/i915/selftests: Include the trace as a debug aide

If we fail to reset the GPU in a timely fashion, dump the GEM trace so
that we can see what operations were in flight when the GPU got stuck.

v2: There's more than one timeout that deserves tracing!
v3: Silence checkpatch by not even using a product at all!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Jeff McGee <jeff.mcgee@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180322074908.10838-1-chris@chris-wilson.co.uk