drm/amdgpu: drm/amdgpu: Handle IOMMU enabled case

Handle all DMA IOMMU group related dependencies before the
group is removed and we try to access it after free.

v2:
Move the actul handling function to TTM

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -3872,6 +3872,8 @@ void amdgpu_device_fini_hw(struct amdgpu_device *adev)
 
 	amdgpu_device_ip_fini_early(adev);
 
+	ttm_device_clear_dma_mappings(&adev->mman.bdev);
+
 	amdgpu_gart_dummy_page_fini(adev);
 
 	amdgpu_device_unmap_mmio(adev);