SPM: Add assets info for partitions

- Define an member named 'assets' in static information for
  assets such generic memory, PPB and platform devices.
- Add macros for loading assets.
- Change SPM logic of scheduling assets.

Change-Id: I1464ea2e70f13cada2cdb45e73a6879e7e6205bb
Signed-off-by: Ken Liu <Ken.Liu@arm.com>
Co-authored-by: Mingyang Sun <Mingyang.Sun@arm.com>
6 files changed