Define docs structure for environments

Adds an extensible structure for documents related to secure processing
environments. The only class of environment currently represented is
Secure Partitions. This change adds a structure to support general
FF-A documents as well as op-tee and hafnium specific documents.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: Ic2fdd792580d711091435716e4b9c863df424149
8 files changed