drm/gem: rip out drm vma accounting for gem mmaps

Doesn't really add anything which can't be figured out through
proc files. And more clearly separates the new gem mmap handling
code from the old drm maps mmap handling code, which is surely a
good thing.

Cc:  Martin Peres <martin.peres@free.fr>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_gem.c

@@ -778,22 +778,14 @@ void drm_gem_vm_open(struct vm_area_struct *vma)
 	struct drm_gem_object *obj = vma->vm_private_data;
 
 	drm_gem_object_reference(obj);
-
-	mutex_lock(&obj->dev->struct_mutex);
-	drm_vm_open_locked(obj->dev, vma);
-	mutex_unlock(&obj->dev->struct_mutex);
 }
 EXPORT_SYMBOL(drm_gem_vm_open);
 
 void drm_gem_vm_close(struct vm_area_struct *vma)
 {
 	struct drm_gem_object *obj = vma->vm_private_data;
-	struct drm_device *dev = obj->dev;
 
-	mutex_lock(&dev->struct_mutex);
-	drm_vm_close_locked(obj->dev, vma);
-	drm_gem_object_unreference(obj);
-	mutex_unlock(&dev->struct_mutex);
+	drm_gem_object_unreference_unlocked(obj);
 }
 EXPORT_SYMBOL(drm_gem_vm_close);
 
@@ -850,7 +842,6 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 	 */
 	drm_gem_object_reference(obj);
 
-	drm_vm_open_locked(dev, vma);
 	return 0;
 }
 EXPORT_SYMBOL(drm_gem_mmap_obj);