drm/ttm: flip over the range manager to self allocated nodes

Start with the range manager to make the resource object the base
class for the allocated nodes.

While at it cleanup a lot of the code around that.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210602100914.46246-2-christian.koenig@amd.com
diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index 83e7258..17a4c5d 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -17,6 +17,8 @@
 #include <drm/drm_prime.h>
 #include <drm/drm_simple_kms_helper.h>
 
+#include <drm/ttm/ttm_range_manager.h>
+
 static const struct drm_gem_object_funcs drm_gem_vram_object_funcs;
 
 /**