Integrate config/kirkstone-santvend-fsl

Commit: config@3830d2fa

bblayers, setup-environment: Add support for seco-mx6-fsl reusing the bblayers_mx8

setup-environment: rename bblayer variants from soc to functionality postfix

Remove the soc type from the bblayer variants and use _fsl in one to describe the functionality. Implement the mapping in the setup-environment script more expressive.