drm/i915/ttm: enable shmem tt backend

Turn on the shmem tt backend, and enable shrinking.
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: NThomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211018091055.1998191-8-matthew.auld@intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm.c

@@ -1113,7 +1113,8 @@ static u64 i915_ttm_mmap_offset(struct drm_i915_gem_object *obj)
 
 static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
 	.name = "i915_gem_object_ttm",
-	.flags = I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST,
+	.flags = I915_GEM_OBJECT_IS_SHRINKABLE |
+		 I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST,
 
 	.get_pages = i915_ttm_get_pages,
 	.put_pages = i915_ttm_put_pages,