drm/amdgpu: Remove duplicate setting of ->need_swiotlb

There's no need to set this before the number of DMA bits has been
properly determined.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c

@@ -1105,7 +1105,6 @@ static int gmc_v8_0_sw_init(void *handle)
 	 */
 	adev->need_dma32 = false;
 	dma_bits = adev->need_dma32 ? 32 : 40;
-	adev->need_swiotlb = drm_get_max_iomem() > ((u64)1 << dma_bits);
 	r = pci_set_dma_mask(adev->pdev, DMA_BIT_MASK(dma_bits));
 	if (r) {
 		adev->need_dma32 = true;