[RFC] Scp 2.11 dts build rfc 003

Created by: mikel-armbb

RFC - for device tree config

Updated version of configuration of SCP firmware build using device tree

Contains documentation in device_tree_support.md, alongside doxygen comments in fwk_devicetree.h and fwk_dt_config_common.h. These will all appear when documentation is built.

Multiple modules supplied as worked examples, using the updated build flow - significant changes since last PR.