linux-yocto-dev: base AUTOREV on specified version

linux-yocto-dev: base AUTOREV on specified version

linux-yocto-dev tracks the latest mainline kernel, and uses
standard/* for that support.

Archived -dev versions are under v<kernel version>/standard/base.

This policy works, except that a released branch will still follow
the new kernel versions, causing potential breakage with newer
kernels than are supported in that release.

Rather than lock the SRCREVs and update branches in old releases,
we can preserve the AUTOREV nature of -dev, and allow them to
switch automatically to the archived branch based on the LINUX_VERSION
in the -dev recipe (which is unchanged in the release branch).

This is consistent with the other branch switching done for the
kernels and with the -dev workflow.

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