conf/layer.conf: Add LAYERSERIES_COMPAT set to thud
conf/layer.conf: Add LAYERSERIES_COMPAT set to thud

Since sumo the LAYERSERIES_COMPAT flag is needed to ensure
layer compatibility so set to thud because will be the next
stable version now master.

Signed-off-by: Aníbal Limón <4676e39632f2bd46f30a0e877949547c228033d4@linaro.org>

96boards/meta-rpb,96boards/meta-rpb