drm/radeon: Use write-combined CPU mappings of ring buffers with PCIe
drm/radeon: Use write-combined CPU mappings of ring buffers with PCIe

PCI GART doesn't support unsnooped access. AGP GART already uses
write-combined CPU mappings.

Signed-off-by: Michel Dänzer <242b79f0804cf52679d58f27ed754158c1323c75@amd.com>
Reviewed-by: Christian König <c7ea837d7a46effe4232b086213468b8b31643bf@amd.com>
Signed-off-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs