Integrate meta-seconorth-mtk/add_fng_boot_files

Commit: seco-ne/yocto/layers/meta-seconorth-mtk@de5bc70e

machine:genio700: Add files required for Flash-N-Go System

The FNG_BOOT_FILES variable is added to the IMAGE_BOOT_FILES. The IMAGE_BOOT_FILES are evaluated in the fngsystem WiC plugin during creation.