Otherwise we try to clear BO_VAs without an address.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=91141Signed-off-by: NChristian König <christian.koenig@amd.com>
Test-by: hadack@gmx.de
Tested-by: NMichel Dänzer <michel.daenzer@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>