futility: vb1_helper: Fix sanity size check for parsing kernel partition
futility: vb1_helper: Fix sanity size check for parsing kernel partition

vbutil_kernel --verify didn't check if the size of the kernel body fit
the file it was in. Now it does.

BRANCH=None
BUG=None
TEST=make runtests

Signed-off-by: Julius Werner <4d12f06cff3725783b352157673a720bc67c4afe@chromium.org>
Change-Id: I9cdfd50bd70b72650cdc0fd62bf59a394746ad84
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2225663
Reviewed-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>

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