drm/i915: Include RING_MODE when dumping the engine state

Knowing the RING_MODE flags is useful for checking the state of the
engine, such as whether the CS is idle after trying to stop the engines
before reset.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026115048.20144-1-chris@chris-wilson.co.uk


Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>