linux-yocto-dev: use versioned branch as default

The -dev kernel used to only have standard/* branches, which were
managed similarly to linux-next. Which means, they are for testing
integration of patches, and are rebased as needed (typically on
version changes).

We now do some leading edge BSP development on the -dev kernel,
so the standard/* branches are not deleted, but are instead
archived with a version prefix v<kernel version>/standard/*

The branch renaming causes problems for maintained releases
(they'll jump forward to newer kernels), and for anything that
wants to specify a particular commit (-dev is AUTOREV by
design).

There's no reason why the branches can't start versioned at
this point, and that solves both problems. So we switch our
default branch to v5.16/standard/base now, and it will be
updated with each new version (we bump the version anyway).

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