drm/i915: Update a couple of hangcheck comments to talk about engines

We still have lots of comments that refer to the old ring when we mean
struct intel_engine_cs and its hardware correspondence. This patch fixes
an instance inside hangcheck to talk about engines.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469432687-22756-10-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469606850-28659-5-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_irq.c

@@ -3140,13 +3140,13 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
 				}
 			} else {
 				/* We always increment the hangcheck score
-				 * if the ring is busy and still processing
+				 * if the engine is busy and still processing
 				 * the same request, so that no single request
 				 * can run indefinitely (such as a chain of
 				 * batches). The only time we do not increment
 				 * the hangcheck score on this ring, if this
-				 * ring is in a legitimate wait for another
-				 * ring. In that case the waiting ring is a
+				 * engine is in a legitimate wait for another
+				 * engine. In that case the waiting engine is a
 				 * victim and we want to be sure we catch the
 				 * right culprit. Then every time we do kick
 				 * the ring, add a small increment to the