feat(imx8mn): add hab and map required memory blocks

In order for HAB to perform operations, memory regions has to be mapped
in TF-A, which HAB ROM code would use internally.

Include those memory blocks for i.MX8MN SoC. Of a special note, the DRAM
block is mapped with complete size available on the platform and uses
MT_RW attributes, this is required to minimize the size of translation
tables and provide a possibility to exchange the execution results
between EL3 and EL1&2, see details in [1].

Link: [1]: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/16880


Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Change-Id: If7a2b718658db452871e1ae56b71a4983e8ef2fe