Platform/RaspberryPi/AcpiTables: add a IORT ACPI table to limit XHCI DMA

Add an IORT table that will limit XHCI DMA to 2 GB, by setting the
DMA width to 31 bits. This is needed for Linux/arm64, which can
only reliably deal with devices that are unable to perform DMA to
the entire 32-bit address range if it can discover their existence
early during boot, and this is before the ACPI interpreter is up
and running (which rules out calling the _DMA method of the XHC0
object)

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Andrei Warkentin <awarkentin@vmware.com>