drm/i915: Use reservation_object_lock()

Replace the calls to ww_mutex_lock(&resv->lock) with the helper
reservation_object_lock(resv) and similarly for unlock.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170221091723.6219-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/i915_gem_batch_pool.c

@@ -122,9 +122,9 @@ i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
 
 		if (tmp->base.size >= size) {
 			/* Clear the set of shared fences early */
-			ww_mutex_lock(&tmp->resv->lock, NULL);
+			reservation_object_lock(tmp->resv, NULL);
 			reservation_object_add_excl_fence(tmp->resv, NULL);
-			ww_mutex_unlock(&tmp->resv->lock);
+			reservation_object_unlock(tmp->resv);
 
 			obj = tmp;
 			break;

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1301,12 +1301,12 @@ static void eb_export_fence(struct drm_i915_gem_object *obj,
 	 * handle an error right now. Worst case should be missed
 	 * synchronisation leading to rendering corruption.
 	 */
-	ww_mutex_lock(&resv->lock, NULL);
+	reservation_object_lock(resv, NULL);
 	if (flags & EXEC_OBJECT_WRITE)
 		reservation_object_add_excl_fence(resv, &req->fence);
 	else if (reservation_object_reserve_shared(resv) == 0)
 		reservation_object_add_shared_fence(resv, &req->fence);
-	ww_mutex_unlock(&resv->lock);
+	reservation_object_unlock(resv);
 }
 
 static void