Platform: Add provisioning api and implementation

Provision data and secrets to OTP memory, where they can later be
retrieved. Used for all data that should be changed on a per-device /
per-implementation basis. Add a cmake option to replace with
platform-specific implementation. Update provisioning documentation.

Change-Id: I0f2e85e93c12bd47b9f68490672d0fc0695e1612
Signed-off-by: Raef Coles <raef.coles@arm.com>
12 files changed