rauc: add bootfs support
This is a fix for issue with ID: 746-001192 RAUC: Handle update of the boot partitions.
Added handling of bootfs partition by RAUC to seco-bundle-edgehog:
- Enabled CONFIG_SQUASHFS; (moved to a separate MR: !460 (merged))
- Added bootfs-image, which will hold IMAGE_BOOT_FILES;
- Created bootfs.vfat image, which will be later used for RAUC bundle;
- Current bootfs image size is hardcoded in recipe.
Edited by Mikhail Vanyulin