Core: Eliminate SPM DB initialising code

This commit modifies template files related to the SPM DB so that
instead of generating code that initialises the DB, a C structure
initialiser is generated directly for the DB.

Change-Id: I88c2cd077a15101d24559027a73716a2f0a5c185
Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>