drm/amdkfd: Remove GWS from process during uninit

If we shut down a process without having destroyed its GWS-using
queues, it is possible that GWS BO will still be in the process
BO list during the gpuvm destruction. This list should be empty
at that time, so we should remove the GWS allocation at the
process uninit point if it is still around.

Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>