vboot/secdata: fix up error reporting in rollback_index.c
vboot/secdata: fix up error reporting in rollback_index.c

Every failure case should output some debug information.

BUG=b:124141368, chromium:972956
TEST=make clean && make runtests
BRANCH=none

Change-Id: I0f178fa72f7e227b3abc22ac1b0d2df5ed4a6dc8
Signed-off-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1738348
Reviewed-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>
Tested-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>
Commit-Queue: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot