drm/i915: Remove unused i915_gem_active_peek_rcu()

This was originally introduced to be used by the busy-ioctl, but in the
end busy ioctl performed a different dance. Since there are no users,
and no likely users, remove an unwanted chunk of the API.

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1470728222-10243-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_request.h

@@ -380,27 +380,6 @@ i915_gem_active_peek(const struct i915_gem_active *active, struct mutex *mutex)
 	return request;
 }
 
-/**
- * i915_gem_active_peek_rcu - report the active request being monitored
- * @active - the active tracker
- *
- * i915_gem_active_peek_rcu() returns the current request being tracked if
- * still active, or NULL. It does not obtain a reference on the request
- * for the caller, and inspection of the request is only valid under
- * the RCU lock.
- */
-static inline struct drm_i915_gem_request *
-i915_gem_active_peek_rcu(const struct i915_gem_active *active)
-{
-	struct drm_i915_gem_request *request;
-
-	request = rcu_dereference(active->request);
-	if (!request || i915_gem_request_completed(request))
-		return NULL;
-
-	return request;
-}
-
 /**
  * i915_gem_active_get - return a reference to the active request
  * @active - the active tracker