Problems with alpha/pci + radeon/ttm

[Matt Turner]

Michael Cree and I have been debugging FDO bug 26403 [1]. I tried
booting with `radeon.test=1` and found this, which I think is related:

> [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0x202000
> [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0x302000
[snip]
> [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0xfd02000
> [drm] Tested GTT->VRAM and VRAM->GTT copy for GTT offset 0xfe02000
> pci_map_single failed: could not allocate dma page tables
> [drm:radeon_ttm_backend_bind] *ERROR* failed to bind 128 pages at 0x0FF02000
> [TTM] Couldn't bind backend.
> radeon 0000:00:07.0: object_init failed for (1048576, 0x00000002)
> [drm:radeon_test_moves] *ERROR* Failed to create GTT object 253
> Error while testing BO move.