drm/i915: Introduce drm_i915_gem_object_ops

In order to specialise functions depending upon the type of object, we
can attach vfuncs to each object via a new ->ops pointer.

For instance, this will be used in future patches to only bind pages from
a dma-buf for the duration that the object is used by the GPU - and so
prevent them from pinning those pages for the entire of the object.

v2: Bonus comments.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 43c9530..e4f1141 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -41,7 +41,7 @@
 	if (ret)
 		return ERR_PTR(ret);
 
-	ret = i915_gem_object_get_pages_gtt(obj);
+	ret = i915_gem_object_get_pages(obj);
 	if (ret) {
 		sg = ERR_PTR(ret);
 		goto out;
@@ -89,7 +89,7 @@
 		goto out_unlock;
 	}
 
-	ret = i915_gem_object_get_pages_gtt(obj);
+	ret = i915_gem_object_get_pages(obj);
 	if (ret) {
 		mutex_unlock(&dev->struct_mutex);
 		return ERR_PTR(ret);