Platform/RPi/AcpiTables: Describe DMA constraints for devices behind GPU

Legacy devices on a Raspberry Pi sit behind GPU/VideoCore and can only
address the first GB of RAM.

This address range of 0xc0000000-0xffffffff requires a translation,
since it is aliased to the first GB of memory 0x00000000-0x3fffffff,
which is what this commit accomplishes by introducing a new "GDV0"
device along with a "_DMA" ResourceTemplate that performs the address
translation.

Note that this translation does not apply to the ARM cores, PCIe,
GENET, and 40-bit DMA channels, that all have a wider view of the
address space.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>