Implement support for 64bit descriptor addresses.
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 20181011021931.4249-8-edgar.iglesias@gmail.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>