drm/amdgpu: Hook up amdgpu_object.c documentation

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Documentation/gpu/amdgpu.rst

@@ -18,6 +18,15 @@ Memory Domains
 .. kernel-doc:: include/uapi/drm/amdgpu_drm.h
    :doc: memory domains
 
+Buffer Objects
+--------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+   :doc: amdgpu_object
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+   :internal:
+
 PRIME Buffer Sharing
 --------------------