vboot/vboot_display: fetch subkey from vboot2 struct

Since CL:1651221, the kernel subkey is stored in vb2_shared_data
and vboot2 workbuf.  Update vboot_display.c to read from this
location accordingly.

BUG=b:124141368, chromium:1038260
TEST=make clean && make runtests
BRANCH=none

Change-Id: Id287ff595bc394d23837e946c0f711b79d2f19ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2051892
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Tested-by: Joel Kitching <kitching@chromium.org>
1 file changed