scripts: make sure hypervisor kernel does not litter rootfs

We do not need hypervisor kernel anywhere but in kernel partition(s), so
stop putting it into rootfs and adjust the base image script to pull it
out of board build directory.

BUG=b:204733585
TEST=Deploy ManaTEE build

Change-Id: I42eec9be15c1cfd8ea86e4430ee79bdff89e6177
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3258484
Commit-Queue: Dmitry Torokhov <dtor@chromium.org>
Tested-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-by: Junichi Uekawa <uekawa@chromium.org>
Reviewed-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Alex Klein <saklein@chromium.org>
2 files changed