dma: Introduce dma_aligned_pow2_mask()

dma: Introduce dma_aligned_pow2_mask()

Currently get_naturally_aligned_size() is used by the intel iommu
to compute the maximum invalidation range based on @size which is
a power of 2 while being aligned with the @start address and less
than the maximum range defined by @gaw.

This helper is also useful for other iommu devices (virtio-iommu,
SMMUv3) to make sure IOMMU UNMAP notifiers only are called with
power of 2 range sizes.

Let's move this latter into dma-helpers.c and rename it into
dma_aligned_pow2_mask(). Also rewrite the helper so that it
accomodates UINT64_MAX values for the size mask and max mask.
It now returns a mask instead of a size. Change the caller.

Signed-off-by: Eric Auger <[email protected]>
Reviewed-by: Peter Xu <[email protected]>
Message-id: 20210309102742[email protected]
Signed-off-by: Peter Maydell <[email protected]>