fix(xilinx): dynamic mmap region for dtb

mmap dtb region before usage and unmap it after usage.
overall size(text,data,bss) of dtb gets reduced by
16 bytes in normal flow and 80 bytes in ddr flow.

Signed-off-by: Amit Nagal <amit.nagal@amd.com>
Change-Id: I411deff57ab141fc2978a2e916aec2d988cb8f9c
3 files changed