feat(arm): add support for loading CONFIG from BL2

This commit introduces a new ARM platform-specific build option called
`ARM_FW_CONFIG_LOAD_ENABLE`. This option enables the loading of the
`fw_config` device tree when resetting to the BL2 scenario.

Additionally, the FW_CONFIG image reference has been added to the
fdts/tbbr_cot_descriptors.dtsi file in order to use in the scenario of
RESET_TO_BL2.

Signed-off-by: Divin Raj <divin.raj@arm.com>
Change-Id: I11de497b7dbb1386ed84d939d6fd2a11856e9e1b
6 files changed