drm/i915: Show CCID in engine dumps

For debugging context issues, knowing what context the GPU is
loading/using is helpful.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180614094103.18025-4-chris@chris-wilson.co.uk