raspberrypi.coffee: Change version to yocto-morty instead of yocto-jethro
raspberrypi.coffee: Change version
to yocto-morty instead of yocto-jethro

We now switch to yocto morty

Signed-off-by: Michal Mazurek <a2df1e659c9fd2578de0a26565357cb273292eeb@resin.io>

resin-os/resin-raspberrypi,resin-os/resin-raspberrypi