[ Upstream commit a28bbd58 ]

Write-combining is a CPU feature. From the GPU POV, these both simply
mean no GPU<->CPU cache coherency.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>