feat(fwu_metadata): add FWU metadata header and build options

Added a firmware update metadata structure as per section 4.1
in the specification document[1].

Also, added the build options used in defining the firmware
update metadata structure.

[1]: https://developer.arm.com/documentation/den0118/a/

Change-Id: I8f43264a46fde777ceae7fd2a5bb0326f1711928
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
3 files changed