linux-yocto/6.12: introduce v6.12 reference kernel

linux-yocto/6.12: introduce v6.12 reference kernel

Introducing the v6.12 reference kernel recipes. This version
has been designated a LTS and will be the default kernel for
the next yocto release.

Some notes:

  - Two fragments are added to linux-yocto-tiny to allow booting
    on qemu out of the box
  - preempt-rt is smaller, but still has patches on top of mainline

This has been boot tested on all architectures, qemu* machine variants,
systemd, sysvinit and both musl and glibc.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>