classes: rename directory to classes-recipe

To match the new feature of bitbake [1] to set scope for classes all classes
of this layer is moved and set to recipe scope.

[1] https://git.openembedded.org/bitbake/commit/?id=f33ce7e742f46635658c400b82558cf822690b5e

Signed-off-by: Peter Bergin <peter@berginkonsult.se>