feat(measured-boot): make event log lib standalone

Remove dependencies on TF-A so the library can be conveniently exported
by other projets. The main changes are to remove explicit error
handling, and ensure that functions instead return errno codes that
consumers can rely on instead. Some work has also been done to make the
function naming a little more consistent.

Change-Id: Ic182dfe7dd6f56a4b73e0da4c9051813938cfe44
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
5 files changed