linux-raspberrypi-dev: Skip if not preferred provider
linux-raspberrypi-dev: Skip if not preferred provider

This should avoid network traffic to resolve ${AUTOREV} unless this
recipe is explicitly selected as the preferred provider of
virtual/kernel.

Signed-off-by: Paul Barker <ea07171fd37de70b22964565a4c2bfd2bb2b3061@toganlabs.com>

agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,d21d3q/meta-raspberrypi,kraj/meta-raspberrypi,d21d3q/meta-raspberrypi,kraj/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,d21d3q/meta-raspberrypi,leon-anavi/meta-raspberrypi,d21d3q/meta-raspberrypi,leon-anavi/meta-raspberrypi,kraj/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,leon-anavi/meta-raspberrypi