added an own kernel defconfig file to "board/raspberrypi3" to allow to tune kernel settings more easily in future.
added an own kernel defconfig file to "board/raspberrypi3" to allow to tune kernel settings more easily in future.

jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic