drm/radeon: do not try to uselessly update virtual memory pagetable

drm/radeon: do not try to uselessly update virtual memory pagetable

commit 3813f5ca9ab7a00e80a17aab34f155453c66c78a upstream.

If a buffer is never bound to a virtual memory pagetable than don't try
to unbind it. Only drawback is that we don't update the pagetable when
unbinding the ib pool buffer which is fine because it only happens at
suspend or module unload/shutdown.

Fixes spurious messages about buffers without VM mappings. E.g.:
radeon 0000:01:00.0: bo ffff88020afac400 don't has a mapping in vm ffff88021ca2b900

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>