linux-lenovo-21bx: upgrade to 6.11

I don't intend to merge this branch until the 6.11 release. It exists to let others help with testing, using mrtest add 5399. If you test this on your x13s and run into regressions, please comment and help me debug it 😁

TODO:

• PD mapper is in kernel now, should drop requirement from lenovo-21bx device pkg (and test), see #2936
• Diff jhovold's config with ours to make sure we have relevant/useful kconfig enabled from his latest
  • jhovold.config (generated from his rc1 defconfig)
  • verdict: Nothing new added/changed