Update the security document to reflect the current state of the
coreboot implementation.
Add more detail and document the change to the public vboot API.
BUG=N/A
TEST=build
Change-Id: I228d0faae0efde70039680a981fea9a436d2384f
Signed-off-by: Wim Vervoorn <wvervoorn@eltan.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38591
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>