allscenarios-zephyr-blueprint-dashboard.conf: Define Zephyr-specific DISTRO...

allscenarios-zephyr-blueprint-dashboard.conf: Define Zephyr-specific DISTRO for Smart Panel Blueprint

This has two advantages:
1. it fixes the build by removing the BBMASK configuration done in the
   main distro configuration files
2. it also provides default MAC addresses in sync with the Linux
   counterparts

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>