drm: store the gem vma offset manager in a typed pointer

This was hidden in a generic void * dev->mm_private. But only ever
used for gem. But thanks to this fake generic pretension no one
noticed that Rob's drm drivers are now all broken.

So just give the offset manager a type pointer and fix up msm, omapdrm
and tilcdc.

v2: Fixup compile fail.

v3: Fixup rebase fail that David spotted.

Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 63ed79f..e6adafc 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -461,7 +461,7 @@
 
 static int msm_mm_show(struct drm_device *dev, struct seq_file *m)
 {
-	return drm_mm_dump_table(m, dev->mm_private);
+	return drm_mm_dump_table(m, &dev->vma_offset_manager->vm_addr_space_mm);
 }
 
 static int msm_fb_show(struct drm_device *dev, struct seq_file *m)