drm/radeon: allways add the VM clear duplicate

We need to allways add the VM clear duplicate of the BO_VA,
no matter what the old status was.

Signed-off-by: Christian König <christian.koenig@amd.com>
Test-by:  <hadack@gmx.de>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>