drm/amdgpu: Remove unnecessary NULL check

A static checker pointed out, that bo_va->base.bo was already derefenced
earlier in the same scope. Therefore this check is unnecessary here.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Fixes: 50661eb1 ("drm/amdgpu: Auto-validate DMABuf imports in compute VMs")
Reviewed-by: Kent Russell <kent.russell@amd.com>
Signed-off-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1477,7 +1477,7 @@ int amdgpu_vm_handle_moved(struct amdgpu_device *adev,
 		/* Remember evicted DMABuf imports in compute VMs for later
 		 * validation
 		 */
-		if (vm->is_compute_context && bo_va->base.bo &&
+		if (vm->is_compute_context &&
 		    bo_va->base.bo->tbo.base.import_attach &&
 		    (!bo_va->base.bo->tbo.resource ||
 		     bo_va->base.bo->tbo.resource->mem_type == TTM_PL_SYSTEM))