iommu: apple-dart: Support specifying the DMA aperture in the DT

Apple DARTs are often connected directly to devices that expect only a
portion of their address space to be used for DMA (for example, because
other ranges are mapped directly to something else). Devices can specify
the start and end of the aperture via "iommus" args if the DART device
node specifies "#iommu-cells = <5>. Aperture start and length are 64-bit
values as apertures above and larger than 4GB are used.
Limit compile testing to 64-bit architectures to avoid warnings in the
calculation of 64-bit dma_addr_t values.

This range *can* be outside of the DART's IAS. In that case, it is
assumed that the hardware truncates addresses and the page tables will
only map the lower bits of the address. However, the specified range
cannot straddle an IAS boundary (you cannot cover more than IAS worth
of address space nor wrap).

This corresponds to the vm-base and vm-size properties on the Apple
device tree side of things.

Co-developed-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Sven Peter <sven@kernel.org>
Signed-off-by: Janne Grunau <j@jannau.net>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

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