iommu: dma: Use of_iommu_get_resv_regions()

iommu: dma: Use of_iommu_get_resv_regions()

For device tree nodes, use the standard of_iommu_get_resv_regions()
implementation to obtain the reserved memory regions associated with a
device.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: devicetree@vger.kernel.org
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20230120174251.4004100-5-thierry.reding@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>