chromeos-init-systemd: Handle missing SecureBoot EFI var

It seems that the SecureBoot EFI var does not appear in efivarfs on new
QEMU on arm64. In this case, SecureBoot is disabled.

BUG=b/192265868
TEST=local BE run
RELEASE_NOTE=None

Change-Id: I963a012c70e04bdab23d8db4935d110fc0afaa7c
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/19131
Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
2 files changed