[PATCH] arm64: avoid increasing DMA masks above what hardware supports

[Nikita Yushchenko]

> Yes, I think that ought to work, although the __iommu_setup_dma_ops()
> call will still want a real size reflecting the default mask

I see iommu_dma_ops do not define set_dma_mask.

So what if setup was done for size reflecting one mask and then driver
changes mask?  Will things still operate correctly?