docs(zynqmp): add ddr address usage

Update documentation for TF-A DDR address range usage when the FSBL is
run on RPU instead of APU.

Change-Id: I223d67c35ac9ce3384820531a7453d3b32a1eb58
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
1 file changed