vboot: update vboot2 functions to use new vb2_error_t

To make explicit when vboot2 error codes should be returned,
use the new vb2_error_t type on all functions which return
VB2_ERROR_* constants.

Additionally, add required vboot submodule commit id e6700f4c:
    2019-07-31 14:12:30 +0800 - (vboot: update vboot2 functions to use new vb2_error_t)

NOTE: This patch was merged separately on the Chromium tree:
https://chromium-review.googlesource.com/c/1728499

BUG=b:124141368, chromium:988410
TEST=make clean && make test-abuild
BRANCH=none

Change-Id: I804c2b407e496d0c8eb9833be629b7c40118415c
Signed-off-by: Joel Kitching <kitching@google.com>
Cq-Depend: chromium:1728292
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34860
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

1 files changed, 0 insertions, 0 deletions

diff --git a/3rdparty/vboot b/3rdparty/vboot
-Subproject a5afd01feb0b4b45adbcd8ab38ab8a2ef2a2ef6
+Subproject e6700f4c70fe72850ae4f3f5df19c9281ebcefc