drm/amdgpu:fix NULL pointer access during drv remove

NULL pointer is because original logic will step into
set_pde_pte() even after the gart.ptr is freed due to
there are twice gart_unbind() on all gart area.

also, there are other minor fixes:
1,since gart_init only create dummy page, the corresponding
gart_fini shouldn't do more like unbinding all GART, this is
unnecessary because in driver fini stage all GART unbinding
had already been done during each IP's SW_FINI (GMC's
SW_FINI is the last one called), so remove the step
for the GART unbinding in gart_fini().

2,gart_fini() is already invoked during each GMC IP's gart_fini
routine,e.g. gmc_vx_0_gart_fini(), so no need to manually
call it during ttm_fini().

3,amdgpu_gem_force_release() should be put ahead of
amdgpu_vm_manager_fini()

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index d49c768..07ecf72 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1402,6 +1402,7 @@ void amdgpu_ttm_fini(struct amdgpu_device *adev)
 
 	amdgpu_ttm_debugfs_fini(adev);
 	amdgpu_bo_free_kernel(&adev->stolen_vga_memory, NULL, NULL);
+	amdgpu_fw_reserve_vram_fini(adev);
 
 	ttm_bo_clean_mm(&adev->mman.bdev, TTM_PL_VRAM);
 	ttm_bo_clean_mm(&adev->mman.bdev, TTM_PL_TT);
@@ -1412,7 +1413,6 @@ void amdgpu_ttm_fini(struct amdgpu_device *adev)
 	if (adev->gds.oa.total_size)
 		ttm_bo_clean_mm(&adev->mman.bdev, AMDGPU_PL_OA);
 	ttm_bo_device_release(&adev->mman.bdev);
-	amdgpu_gart_fini(adev);
 	amdgpu_ttm_global_fini(adev);
 	adev->mman.initialized = false;
 	DRM_INFO("amdgpu: ttm finalized\n");