security/vboot: Add measured boot mode

* Introduce a measured boot mode into vboot.
* Add hook for stage measurements in prog_loader and cbfs.
* Implement and hook-up CRTM in vboot and check for suspend.

Change-Id: I339a2f1051e44f36aba9f99828f130592a09355e
Signed-off-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/c/29547
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/security.md

@@ -0,0 +1,5 @@
+# Security
+
+## Google VBoot2 Measured boot extension
+
+- [Measured Boot](vboot/measured_boot.md)