drm/nouveau: enable the ttm dma pool when swiotlb is active V3

If the card is capable of more than 32-bit, then use the default
TTM page pool code which allocates from anywhere in the memory.

Note: If the 'ttm.no_dma' parameter is set, the override is ignored
and the default TTM pool is used.

V2 use pci_set_consistent_dma_mask
V3 Rebase on top of no memory account changes (where/when is my
   delorean when i need it ?)

CC: Ben Skeggs <bskeggs@redhat.com>
CC: Francisco Jerez <currojerez@riseup.net>
CC: Dave Airlie <airlied@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>

drivers/gpu/drm/nouveau/nouveau_mem.c

@@ -407,6 +407,12 @@ nouveau_mem_vram_init(struct drm_device *dev)
 	ret = pci_set_dma_mask(dev->pdev, DMA_BIT_MASK(dma_bits));
 	if (ret)
 		return ret;
+	ret = pci_set_consistent_dma_mask(dev->pdev, DMA_BIT_MASK(dma_bits));
+	if (ret) {
+		/* Reset to default value. */
+		pci_set_consistent_dma_mask(dev->pdev, DMA_BIT_MASK(32));
+	}
+
 
 	ret = nouveau_ttm_global_init(dev_priv);
 	if (ret)