3rdparty/vboot: Add vboot

This allows providing a verified boot mechanism in the
default distribution, as well as reusing vboot code like
its crypto primitives for reasonably secure checksums over
CBFS files.

Change-Id: I729b249776b2bf7aa4b2f69bb18ec655b9b08d90
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10107
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/.gitmodules b/.gitmodules
index cf32923..7d40675 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -6,3 +6,6 @@
 [submodule "util/nvidia-cbootimage"]
 	path = util/nvidia/cbootimage
 	url = ../nvidia-cbootimage.git
+[submodule "vboot"]
+	path = 3rdparty/vboot
+	url = ../vboot.git