unix: update to kernel Linux 6.12

Change-Id: I7c8157d5f1b597b6ae249b20866bbad918b46fa4
GitHub-Last-Rev: 0bbc2efbab1d85249d81a200b7821b7901cea2dd
GitHub-Pull-Request: golang/sys#238
Reviewed-on: https://go-review.googlesource.com/c/sys/+/629075
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>