project-lakitu: Remove collecting root devices using lsblk

There is no need to lsblk for boot disks since it's
partition scheme is well defined. This is to improve the performance
of the NPD.

BUG=b/188217381
TEST=presubmit and manual
RELEASE_NOTE=None

Change-Id: I9ed015642ddc9467eaf239512dc65cfd9380fc18
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/17850
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-by: Roy Yang <royyang@google.com>
2 files changed