drm/amdgpu: remove tlb flush in amdgpu_gtt_mgr_recover

At this point the gart is not set up, there's no point to invalidate tlb
here and it could even be harmful.

Signed-off-by: Yunxiang Li <Yunxiang.Li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>