kexec-tools: upgraded package to upstream

Upgraded sys-apps/kexec-tools to version 2.0.20-r3
Previous version didn't have support for kexec_file_load syscall on ARM64.

BUG=b/179916171
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I8eabd27e443413aa64a77b1db3d2e09ce737e74e
Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/portage-stable/+/12470
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Roy Yang <royyang@google.com>
9 files changed