vboot: rename VbError_t typedef to vb2_error_t

As part of the conversion of error codes from vboot1 to vboot2,
replace all instances of VbError_t with vb2_error_t.

vboot2 currently uses the int type for return values, but we
would like to implement the use of vb2_error_t instead, which is
potentially clearer than simply using an int.  Existing functions
will be converted to use vb2_error_t in a subsequent CL.

BUG=b:124141368, chromium:988410
TEST=make clean && make runtests
BRANCH=none

Change-Id: Iee90d9a1f46bcf5f088e981ba6ddbcf886ff0f18
Signed-off-by: Joel Kitching <kitching@google.com>
Cq-Depend: chromium:1728112
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1722914
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Tested-by: Joel Kitching <kitching@chromium.org>
31 files changed