gpu: ion: Change from uncached to buffered mapping

PMEM uses buffered mappings when PMEM device is
opened with O_SYNC flag. ION should have the same
behavior as PMEM.

Change ION to provide buffered mappings instead
of uncached when the O_DSYNC flag is used when
opening the ION device.

CRs-fixed: 335827
Change-Id: I369a35a2ff68adc8339380dfbb7721e3d361ee69
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
diff --git a/drivers/gpu/ion/ion_iommu_heap.c b/drivers/gpu/ion/ion_iommu_heap.c
index d37a811..2f9e80c 100644
--- a/drivers/gpu/ion/ion_iommu_heap.c
+++ b/drivers/gpu/ion/ion_iommu_heap.c
@@ -136,7 +136,7 @@
 		return -EINVAL;
 
 	if (!ION_IS_CACHED(flags))
-		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 
 	for (i = 0; i < data->nrpages; i++)
 		if (vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,