iommu: Map reserved memory as cacheable if device is coherent

Check if the device is marked as DMA coherent in the DT and if so,
map its reserved memory as cacheable in the IOMMU.
This fixes the recently added IOMMU reserved memory support which
uses IOMMU_RESV_DIRECT without properly building the PROT for the
mapping.

Fixes: a5bf3cfc ("iommu: Implement of_iommu_get_resv_regions()")
Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20230926152600.8749-1-laurentiu.tudor@nxp.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/of_iommu.c

@@ -254,6 +254,9 @@ void of_iommu_get_resv_regions(struct device *dev, struct list_head *list)
 				phys_addr_t iova;
 				size_t length;
 
+				if (of_dma_is_coherent(dev->of_node))
+					prot |= IOMMU_CACHE;
+
 				maps = of_translate_dma_region(np, maps, &iova, &length);
 				type = iommu_resv_region_get_type(dev, &phys, iova, length);