drm/amdgpu: add AMDGPU_BO_INVALID_OFFSET

An invalid offset to be used by custom VRAM/GGT manager when we
don't have an offset for an BO.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
index 3032c54..8255034 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
@@ -31,6 +31,8 @@
 #include <drm/amdgpu_drm.h>
 #include "amdgpu.h"
 
+#define AMDGPU_BO_INVALID_OFFSET	LONG_MAX
+
 /**
  * amdgpu_mem_type_to_domain - return domain corresponding to mem_type
  * @mem_type:	ttm memory type