layer.conf: Add LAYERSERIES_COMPAT entry
layer.conf: Add LAYERSERIES_COMPAT entry

In preparation for Sumo release, add a LAYERSERIES_COMPAT definition.

In Sumo, if LAYERSERIES_COMPAT is not defined, bitbake will display
following complaint:

  WARNING: Layer atmel should set LAYERSERIES_COMPAT_atmel in its
           conf/layer.conf file to list the core layer names it is
           compatible with.

Signed-off-by: Niko Mauno <ad7952411f0891f452fe24df4bbaacb4612f5dc1@vaisala.com>

alexandrebelloni/meta-atmel,linux4sam/meta-atmel,alexandrebelloni/meta-atmel,linux4sam/meta-atmel,linux4sam/meta-atmel,alexandrebelloni/meta-atmel,linux4sam/meta-atmel,linux4sam/meta-atmel